diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSlim4ServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSlim4ServerCodegen.java
index b2b8fd31e76..4ec5c1f1166 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSlim4ServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSlim4ServerCodegen.java
@@ -42,6 +42,8 @@ public class PhpSlim4ServerCodegen extends PhpSlimServerCodegen {
     protected String psr7Implementation = "slim-psr7";
     protected String mockDirName = "Mock";
     protected String mockPackage = "";
+    protected String utilsDirName = "Utils";
+    protected String utilsPackage = "";
 
     public PhpSlim4ServerCodegen() {
         super();
@@ -51,6 +53,7 @@ public class PhpSlim4ServerCodegen extends PhpSlimServerCodegen {
                 .build();
 
         mockPackage = invokerPackage + "\\" + mockDirName;
+        utilsPackage = invokerPackage + "\\" + utilsDirName;
         outputFolder = "generated-code" + File.separator + "slim4";
         embeddedTemplateDir = templateDir = "php-slim4-server";
 
@@ -86,8 +89,9 @@ public class PhpSlim4ServerCodegen extends PhpSlimServerCodegen {
         super.processOpts();
 
         if (additionalProperties.containsKey(CodegenConstants.INVOKER_PACKAGE)) {
-            // Update the invokerPackage for the default mockPackage
+            // Update mockPackage and utilsPackage
             mockPackage = invokerPackage + "\\" + mockDirName;
+            utilsPackage = invokerPackage + "\\" + utilsDirName;
         }
 
         // make mock src path available in mustache template
@@ -95,6 +99,11 @@ public class PhpSlim4ServerCodegen extends PhpSlimServerCodegen {
         additionalProperties.put("mockSrcPath", "./" + toSrcPath(mockPackage, srcBasePath));
         additionalProperties.put("mockTestPath", "./" + toSrcPath(mockPackage, testBasePath));
 
+        // same for utils package
+        additionalProperties.put("utilsPackage", utilsPackage);
+        additionalProperties.put("utilsSrcPath", "./" + toSrcPath(utilsPackage, srcBasePath));
+        additionalProperties.put("utilsTestPath", "./" + toSrcPath(utilsPackage, testBasePath));
+
         if (additionalProperties.containsKey(PSR7_IMPLEMENTATION)) {
             this.setPsr7Implementation((String) additionalProperties.get(PSR7_IMPLEMENTATION));
         }
@@ -132,6 +141,12 @@ public class PhpSlim4ServerCodegen extends PhpSlimServerCodegen {
         supportingFiles.add(new SupportingFile("openapi_data_mocker_interface.mustache", toSrcPath(mockPackage, srcBasePath), toInterfaceName("OpenApiDataMocker") + ".php"));
         supportingFiles.add(new SupportingFile("openapi_data_mocker.mustache", toSrcPath(mockPackage, srcBasePath), "OpenApiDataMocker.php"));
         supportingFiles.add(new SupportingFile("openapi_data_mocker_test.mustache", toSrcPath(mockPackage, testBasePath), "OpenApiDataMockerTest.php"));
+
+        // traits of ported utils
+        supportingFiles.add(new SupportingFile("string_utils_trait.mustache", toSrcPath(utilsPackage, srcBasePath), toTraitName("StringUtils") + ".php"));
+        supportingFiles.add(new SupportingFile("string_utils_trait_test.mustache", toSrcPath(utilsPackage, testBasePath), toTraitName("StringUtils") + "Test.php"));
+        supportingFiles.add(new SupportingFile("model_utils_trait.mustache", toSrcPath(utilsPackage, srcBasePath), toTraitName("ModelUtils") + ".php"));
+        supportingFiles.add(new SupportingFile("model_utils_trait_test.mustache", toSrcPath(utilsPackage, testBasePath), toTraitName("ModelUtils") + "Test.php"));
     }
 
     /**
diff --git a/modules/openapi-generator/src/main/resources/php-slim4-server/composer.mustache b/modules/openapi-generator/src/main/resources/php-slim4-server/composer.mustache
index cc4f128875f..68b2c89e92f 100644
--- a/modules/openapi-generator/src/main/resources/php-slim4-server/composer.mustache
+++ b/modules/openapi-generator/src/main/resources/php-slim4-server/composer.mustache
@@ -43,11 +43,13 @@
     "test": [
       "@test-apis",
       "@test-models",
-      "@test-mock"
+      "@test-mock",
+      "@test-utils"
     ],
     "test-apis": "phpunit --testsuite Apis",
     "test-models": "phpunit --testsuite Models",
     "test-mock": "phpunit --testsuite Mock",
+    "test-utils": "phpunit --testsuite Utils",
     "phpcs": "phpcs",
     "phplint": "phplint ./ --exclude=vendor"
   }
diff --git a/modules/openapi-generator/src/main/resources/php-slim4-server/model_utils_trait.mustache b/modules/openapi-generator/src/main/resources/php-slim4-server/model_utils_trait.mustache
new file mode 100644
index 00000000000..7f068fa1c77
--- /dev/null
+++ b/modules/openapi-generator/src/main/resources/php-slim4-server/model_utils_trait.mustache
@@ -0,0 +1,132 @@
+<?php
+
+/**
+ * {{traitNamePrefix}}ModelUtils{{traitNameSuffix}}
+ *
+ * PHP version 7.1
+ *
+ * @package {{invokerPackage}}
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+
+/**{{#apiInfo}}{{#appName}}
+ * {{{appName}}}
+ *
+ {{/appName}}
+ {{#appDescription}}
+ * {{{appDescription}}}
+ {{/appDescription}}
+ {{#version}}
+ * The version of the OpenAPI document: {{{version}}}
+ {{/version}}
+ {{#infoEmail}}
+ * Contact: {{{infoEmail}}}
+ {{/infoEmail}}
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+/**
+ * NOTE: This class is auto generated by the openapi generator program.
+ * https://github.com/openapitools/openapi-generator
+ * Do not edit the class manually.
+ */
+namespace {{utilsPackage}};
+
+use {{utilsPackage}}\{{traitNamePrefix}}StringUtils{{traitNameSuffix}};
+
+/**
+ * {{traitNamePrefix}}ModelUtils{{traitNameSuffix}} Class Doc Comment
+ * This class duplicates functionality of ModelUtils.java and AbstractPhpCodegen.java classes.
+ *
+ * @package {{utilsPackage}}
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+trait {{traitNamePrefix}}ModelUtils{{traitNameSuffix}}
+{
+    use {{traitNamePrefix}}StringUtils{{traitNameSuffix}};
+
+    /**
+     * Parses model class name from provided ref.
+     * @link https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.1.md#reference-object
+     * This method doesn't check that class exists and autoloaded.
+     * This is recreated method of @link modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java class.
+     *
+     * @param string $ref Reference, eg. #/components/schemas/Pet
+     *
+     * @return string|null classname or null on fail
+     */
+    public static function getSimpleRef($ref)
+    {
+        $model = null;
+        if (stripos($ref, '#/components/') === 0) {
+            // starts with #/components/
+            $model = substr($ref, strrpos($ref, '/') + 1);
+        } elseif (stripos($ref, '#/definitions/') === 0) {
+            // starts with #/definitions/
+            $model = substr($ref, strrpos($ref, '/') + 1);
+        }
+
+        return $model;
+    }
+
+    /**
+     * Output the proper model name (capitalized).
+     * In case the name belongs to the TypeSystem it won't be renamed.
+     * This is recreated method of @link modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java class.
+     *
+     * @param string      $name            the name of the model
+     * @param string|null $modelNamePrefix modelNamePrefix generator option
+     * @param string|null $modelNameSuffix modelNameSuffix generator option
+     *
+     * @return string capitalized model name
+     */
+    public static function toModelName(
+        $name,
+        $modelNamePrefix = {{#modelNamePrefix}}'{{modelNamePrefix}}'{{/modelNamePrefix}}{{^modelNamePrefix}}null{{/modelNamePrefix}},
+        $modelNameSuffix = {{#modelNameSuffix}}'{{modelNameSuffix}}'{{/modelNameSuffix}}{{^modelNameSuffix}}null{{/modelNameSuffix}}
+    ) {
+        if (is_string($name) === false  || empty($name)) {
+            return null;
+        }
+
+        // remove [
+        $name = str_replace(']', '', $name);
+
+        // Note: backslash ("\\") is allowed for e.g. "\\DateTime"
+        $name = preg_replace('/[^\w\\\\]+/', '_', $name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+
+        // remove underscores from start and end
+        $name = trim($name, '_');
+
+        // remove dollar sign
+        $name = str_replace('$', '', $name);
+
+        // model name cannot use reserved keyword
+        if (self::isReservedWord($name)) {
+            $name = 'model_' . $name; // e.g. return => ModelReturn (after camelize)
+        }
+
+        // model name starts with number
+        if (preg_match('/^\d.*/', $name) === 1) {
+            $name = 'model_' . $name; // e.g. 200Response => Model200Response (after camelize)
+        }
+
+        // add prefix and/or suffic only if name does not start wth \ (e.g. \DateTime)
+        if (preg_match('/^\\\\.*/', $name) !== 1) {
+            if (is_string($modelNamePrefix) && !empty($modelNamePrefix)) {
+                $name = $modelNamePrefix . '_' . $name;
+            }
+
+            if (is_string($modelNameSuffix) && !empty($modelNameSuffix)) {
+                $name = $name . '_' . $modelNameSuffix;
+            }
+        }
+
+        // camelize the model name
+        // phone_number => PhoneNumber
+        return self::camelize($name);
+    }
+}
+{{/apiInfo}}
diff --git a/modules/openapi-generator/src/main/resources/php-slim4-server/model_utils_trait_test.mustache b/modules/openapi-generator/src/main/resources/php-slim4-server/model_utils_trait_test.mustache
new file mode 100644
index 00000000000..f3d365eba67
--- /dev/null
+++ b/modules/openapi-generator/src/main/resources/php-slim4-server/model_utils_trait_test.mustache
@@ -0,0 +1,111 @@
+<?php
+
+/**
+ * {{traitNamePrefix}}ModelUtils{{traitNameSuffix}}Test
+ *
+ * PHP version 7.1
+ *
+ * @package {{invokerPackage}}
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+
+/**{{#apiInfo}}{{#appName}}
+ * {{{appName}}}
+ *
+ {{/appName}}
+ {{#appDescription}}
+ * {{{appDescription}}}
+ {{/appDescription}}
+ {{#version}}
+ * The version of the OpenAPI document: {{{version}}}
+ {{/version}}
+ {{#infoEmail}}
+ * Contact: {{{infoEmail}}}
+ {{/infoEmail}}
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+/**
+ * NOTE: This class is auto generated by the openapi generator program.
+ * https://github.com/openapitools/openapi-generator
+ * Do not edit the class manually.
+ */
+namespace {{utilsPackage}};
+
+use {{utilsPackage}}\{{traitNamePrefix}}ModelUtils{{traitNameSuffix}} as ModelUtils;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * {{traitNamePrefix}}ModelUtils{{traitNameSuffix}}Test Class Doc Comment
+ *
+ * @package {{utilsPackage}}
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ * @coversDefaultClass \{{utilsPackage}}\{{traitNamePrefix}}ModelUtils{{traitNameSuffix}}
+ */
+class {{traitNamePrefix}}ModelUtils{{traitNameSuffix}}Test extends TestCase
+{
+    /**
+     * @covers ::getSimpleRef
+     * @dataProvider provideRefs
+     */
+    public function testGetSimpleRef($ref, $expectedRef)
+    {
+        $this->assertSame($expectedRef, ModelUtils::getSimpleRef($ref));
+    }
+
+    public function provideRefs()
+    {
+        return [
+            'Reference Object OAS 3.0' => [
+                '#/components/schemas/Pet', 'Pet',
+            ],
+            'Reference Object Swagger 2.0' => [
+                '#/definitions/Pet', 'Pet',
+            ],
+            'Underscored classname' => [
+                '#/components/schemas/_foobar_Objects', '_foobar_Objects',
+            ],
+            'Relative Documents With Embedded Schema' => [
+                'definitions.json#/Pet', null,
+            ],
+            'null as argument' => [
+                null, null,
+            ],
+            'number as argument' => [
+                156, null,
+            ],
+        ];
+    }
+
+    /**
+     * @covers ::toModelName
+     * @dataProvider provideModelNames
+     */
+    public function testToModelName($name, $prefix, $suffix, $expectedModel)
+    {
+        $this->assertSame($expectedModel, ModelUtils::toModelName($name, $prefix, $suffix));
+    }
+
+    public function provideModelNames()
+    {
+        return [
+            // fixtures from modules/openapi-generator/src/test/java/org/openapitools/codegen/utils/StringUtilsTest.java
+            ['abcd', null, null, 'Abcd'],
+            ['some-value', null, null, 'SomeValue'],
+            ['some_value', null, null, 'SomeValue'],
+            ['$type', null, null, 'Type'],
+            ['123', null, null, 'Model123'],
+            ['$123', null, null, 'Model123'],
+            ['return', null, null, 'ModelReturn'],
+            ['200Response', null, null, 'Model200Response'],
+            ['abcd', 'SuperModel', null, 'SuperModelAbcd'],
+            ['abcd', null, 'WithEnd', 'AbcdWithEnd'],
+            ['abcd', 'WithStart', 'AndEnd', 'WithStartAbcdAndEnd'],
+            ['_foobar_Objects', null, null, 'FoobarObjects'],
+            [null, null, null, null],
+        ];
+    }
+}
+{{/apiInfo}}
diff --git a/modules/openapi-generator/src/main/resources/php-slim4-server/phpunit.xml.mustache b/modules/openapi-generator/src/main/resources/php-slim4-server/phpunit.xml.mustache
index 81e19e73605..82f86439083 100644
--- a/modules/openapi-generator/src/main/resources/php-slim4-server/phpunit.xml.mustache
+++ b/modules/openapi-generator/src/main/resources/php-slim4-server/phpunit.xml.mustache
@@ -20,12 +20,16 @@
         <testsuite name="Mock">
             <directory>{{mockTestPath}}</directory>
         </testsuite>
+        <testsuite name="Utils">
+            <directory>{{utilsTestPath}}</directory>
+        </testsuite>
     </testsuites>
     <filter>
         <whitelist processUncoveredFilesFromWhitelist="true">
             <directory suffix=".php">{{apiSrcPath}}</directory>
             <directory suffix=".php">{{modelSrcPath}}</directory>
             <directory suffix=".php">{{mockSrcPath}}</directory>
+            <directory suffix=".php">{{utilsSrcPath}}</directory>
         </whitelist>
     </filter>
     <php>
diff --git a/modules/openapi-generator/src/main/resources/php-slim4-server/string_utils_trait.mustache b/modules/openapi-generator/src/main/resources/php-slim4-server/string_utils_trait.mustache
new file mode 100644
index 00000000000..6d5d15feff6
--- /dev/null
+++ b/modules/openapi-generator/src/main/resources/php-slim4-server/string_utils_trait.mustache
@@ -0,0 +1,141 @@
+<?php
+
+/**
+ * {{traitNamePrefix}}StringUtils{{traitNameSuffix}}
+ *
+ * PHP version 7.1
+ *
+ * @package {{invokerPackage}}
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+
+/**{{#apiInfo}}{{#appName}}
+ * {{{appName}}}
+ *
+ {{/appName}}
+ {{#appDescription}}
+ * {{{appDescription}}}
+ {{/appDescription}}
+ {{#version}}
+ * The version of the OpenAPI document: {{{version}}}
+ {{/version}}
+ {{#infoEmail}}
+ * Contact: {{{infoEmail}}}
+ {{/infoEmail}}
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+/**
+ * NOTE: This class is auto generated by the openapi generator program.
+ * https://github.com/openapitools/openapi-generator
+ * Do not edit the class manually.
+ */
+namespace {{utilsPackage}};
+
+/**
+ * {{traitNamePrefix}}StringUtils{{traitNameSuffix}} Class Doc Comment
+ * This class duplicates functionality of StringUtils.java and AbstractPhpCodegen.java classes.
+ *
+ * @package {{utilsPackage}}
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+trait {{traitNamePrefix}}StringUtils{{traitNameSuffix}}
+{
+    /**
+     * Camelize name (parameter, property, method, etc)
+     * This is recreated method of @link modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/StringUtils.java class.
+     *
+     * @param string $word                 string to be camelize
+     * @param bool   $lowercaseFirstLetter lower case for first letter if set to true
+     *
+     * @return string camelized string
+     */
+    public static function camelize($word, $lowercaseFirstLetter = false)
+    {
+        // Replace all slashes with dots (package separator)
+        $p = '/\/(.?)/';
+        $word = preg_replace($p, '.$1', $word);
+
+        // case out dots
+        $parts = explode('.', $word);
+        $str = '';
+        foreach ($parts as $z) {
+            if (strlen($z) > 0) {
+                $str .= strtoupper(substr($z, 0, 1)) . substr($z, 1);
+            }
+        }
+        $word = $str;
+
+        // Uppercase the class name.
+        $p = '/(\.?)(\w)([^\.]*)$/';
+        $word = preg_replace_callback($p, function ($matches) {
+            $rep = $matches[1] . strtoupper($matches[2]) . $matches[3];
+            $rep = preg_replace('/\$/', '\\\$', $rep);
+            return $rep;
+        }, $word);
+
+        // Remove all underscores (underscore_case to camelCase)
+        $p = '/(_)(.)/';
+        while (preg_match($p, $word, $matches) === 1) {
+            $original = $matches[2][0];
+            $upperCase = strtoupper($original);
+            if ($original === $upperCase) {
+                $word = preg_replace($p, '$2', $word);
+            } else {
+                $word = preg_replace($p, $upperCase, $word);
+            }
+        }
+
+        // Remove all hyphens (hyphen-case to camelCase)
+        $p = '/(-)(.)/';
+        while (preg_match($p, $word, $matches) === 1) {
+            $upperCase = strtoupper($matches[2][0]);
+            $word = preg_replace($p, $upperCase, $word);
+        }
+
+        if ($lowercaseFirstLetter === true && strlen($word) > 0) {
+            $i = 0;
+            $charAt = substr($word, $i, 1);
+            while (
+                $i + 1 < strlen($word)
+                && !(
+                    ($charAt >= 'a' && $charAt <= 'z')
+                    || ($charAt >= 'A' && $charAt <= 'Z')
+                )
+            ) {
+                $i++;
+                $charAt = substr($word, $i, 1);
+            }
+            $i++;
+            $word = strtolower(substr($word, 0, $i)) . substr($word, $i);
+        }
+
+        // remove all underscore
+        $word = str_replace('_', '', $word);
+
+        return $word;
+    }
+
+    /**
+     * Checks whether string is reserved php keyword.
+     * This is recreated method of @link modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java class.
+     *
+     * @param string $word Checked string
+     *
+     * @return bool
+     */
+    public static function isReservedWord($word)
+    {
+        if (is_string($word) === false) {
+            return false;
+        }
+        // __halt_compiler is ommited because class names with underscores not allowed anyway
+        return in_array(
+            strtolower($word),
+            ['abstract', 'and', 'array', 'as', 'break', 'callable', 'case', 'catch', 'class', 'clone', 'const', 'continue', 'declare', 'default', 'die', 'do', 'echo', 'else', 'elseif', 'empty', 'enddeclare', 'endfor', 'endforeach', 'endif', 'endswitch', 'endwhile', 'eval', 'exit', 'extends', 'final', 'for', 'foreach', 'function', 'global', 'goto', 'if', 'implements', 'include', 'include_once', 'instanceof', 'insteadof', 'interface', 'isset', 'list', 'namespace', 'new', 'or', 'print', 'private', 'protected', 'public', 'require', 'require_once', 'return', 'static', 'switch', 'throw', 'trait', 'try', 'unset', 'use', 'var', 'while', 'xor']
+        );
+    }
+}
+{{/apiInfo}}
diff --git a/modules/openapi-generator/src/main/resources/php-slim4-server/string_utils_trait_test.mustache b/modules/openapi-generator/src/main/resources/php-slim4-server/string_utils_trait_test.mustache
new file mode 100644
index 00000000000..9698d6bcf6c
--- /dev/null
+++ b/modules/openapi-generator/src/main/resources/php-slim4-server/string_utils_trait_test.mustache
@@ -0,0 +1,108 @@
+<?php
+
+/**
+ * {{traitNamePrefix}}StringUtils{{traitNameSuffix}}Test
+ *
+ * PHP version 7.1
+ *
+ * @package {{invokerPackage}}
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+
+/**{{#apiInfo}}{{#appName}}
+ * {{{appName}}}
+ *
+ {{/appName}}
+ {{#appDescription}}
+ * {{{appDescription}}}
+ {{/appDescription}}
+ {{#version}}
+ * The version of the OpenAPI document: {{{version}}}
+ {{/version}}
+ {{#infoEmail}}
+ * Contact: {{{infoEmail}}}
+ {{/infoEmail}}
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+/**
+ * NOTE: This class is auto generated by the openapi generator program.
+ * https://github.com/openapitools/openapi-generator
+ * Do not edit the class manually.
+ */
+namespace {{utilsPackage}};
+
+use {{utilsPackage}}\{{traitNamePrefix}}StringUtils{{traitNameSuffix}} as StringUtils;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * {{traitNamePrefix}}StringUtils{{traitNameSuffix}}Test Class Doc Comment
+ *
+ * @package {{utilsPackage}}
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ * @coversDefaultClass \{{utilsPackage}}\{{traitNamePrefix}}StringUtils{{traitNameSuffix}}
+ */
+class {{traitNamePrefix}}StringUtils{{traitNameSuffix}}Test extends TestCase
+{
+    /**
+     * @covers ::camelize
+     * @dataProvider provideWordsForCamelizeTest
+     */
+    public function testCamelize($word, $lowercaseFirstLetter, $expectedWord)
+    {
+        $this->assertSame($expectedWord, StringUtils::camelize($word, $lowercaseFirstLetter));
+    }
+
+    public function provideWordsForCamelizeTest()
+    {
+        return [
+            // fixtures from modules/openapi-generator/src/test/java/org/openapitools/codegen/utils/StringUtilsTest.java
+            ['openApiServer/model/pet', null, 'OpenApiServerModelPet'],
+            ['abcd', null, 'Abcd'],
+            ['some-value', null, 'SomeValue'],
+            ['some-Value', null, 'SomeValue'],
+            ['some_value', null, 'SomeValue'],
+            ['some_Value', null, 'SomeValue'],
+            ['$type', null, '$Type'],
+
+            ['abcd', true, 'abcd'],
+            ['some-value', true, 'someValue'],
+            ['some_value', true, 'someValue'],
+            ['Abcd', true, 'abcd'],
+            ['$type', true, '$type'],
+
+            ['123', true, '123'],
+            ['$123', true, '$123'],
+        ];
+    }
+
+    /**
+     * @covers ::isReservedWord
+     * @dataProvider provideWordsForIsReservedTest
+     */
+    public function testisReservedWord($word, $expected)
+    {
+        $this->assertSame($expected, StringUtils::isReservedWord($word));
+    }
+
+    public function provideWordsForIsReservedTest()
+    {
+        return [
+            ['return', true],
+            ['switch', true],
+            ['class', true],
+            ['interface', true],
+            ['ABSTRACT', true],
+            ['Trait', true],
+            ['final', true],
+            ['foobar', false],
+            ['DateTime', false],
+            ['Pet', false],
+            [123, false],
+            [null, false],
+        ];
+    }
+}
+{{/apiInfo}}
diff --git a/samples/server/petstore/php-slim4/composer.json b/samples/server/petstore/php-slim4/composer.json
index 4a45af2568d..d7d8142f6d1 100644
--- a/samples/server/petstore/php-slim4/composer.json
+++ b/samples/server/petstore/php-slim4/composer.json
@@ -30,11 +30,13 @@
     "test": [
       "@test-apis",
       "@test-models",
-      "@test-mock"
+      "@test-mock",
+      "@test-utils"
     ],
     "test-apis": "phpunit --testsuite Apis",
     "test-models": "phpunit --testsuite Models",
     "test-mock": "phpunit --testsuite Mock",
+    "test-utils": "phpunit --testsuite Utils",
     "phpcs": "phpcs",
     "phplint": "phplint ./ --exclude=vendor"
   }
diff --git a/samples/server/petstore/php-slim4/lib/Utils/ModelUtilsTrait.php b/samples/server/petstore/php-slim4/lib/Utils/ModelUtilsTrait.php
new file mode 100644
index 00000000000..97bb2ae884a
--- /dev/null
+++ b/samples/server/petstore/php-slim4/lib/Utils/ModelUtilsTrait.php
@@ -0,0 +1,123 @@
+<?php
+
+/**
+ * ModelUtilsTrait
+ *
+ * PHP version 7.1
+ *
+ * @package OpenAPIServer
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+
+/**
+ * OpenAPI Petstore
+ *
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ * The version of the OpenAPI document: 1.0.0
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+/**
+ * NOTE: This class is auto generated by the openapi generator program.
+ * https://github.com/openapitools/openapi-generator
+ * Do not edit the class manually.
+ */
+namespace OpenAPIServer\Utils;
+
+use OpenAPIServer\Utils\StringUtilsTrait;
+
+/**
+ * ModelUtilsTrait Class Doc Comment
+ * This class duplicates functionality of ModelUtils.java and AbstractPhpCodegen.java classes.
+ *
+ * @package OpenAPIServer\Utils
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+trait ModelUtilsTrait
+{
+    use StringUtilsTrait;
+
+    /**
+     * Parses model class name from provided ref.
+     * @link https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.1.md#reference-object
+     * This method doesn't check that class exists and autoloaded.
+     * This is recreated method of @link modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java class.
+     *
+     * @param string $ref Reference, eg. #/components/schemas/Pet
+     *
+     * @return string|null classname or null on fail
+     */
+    public static function getSimpleRef($ref)
+    {
+        $model = null;
+        if (stripos($ref, '#/components/') === 0) {
+            // starts with #/components/
+            $model = substr($ref, strrpos($ref, '/') + 1);
+        } elseif (stripos($ref, '#/definitions/') === 0) {
+            // starts with #/definitions/
+            $model = substr($ref, strrpos($ref, '/') + 1);
+        }
+
+        return $model;
+    }
+
+    /**
+     * Output the proper model name (capitalized).
+     * In case the name belongs to the TypeSystem it won't be renamed.
+     * This is recreated method of @link modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java class.
+     *
+     * @param string      $name            the name of the model
+     * @param string|null $modelNamePrefix modelNamePrefix generator option
+     * @param string|null $modelNameSuffix modelNameSuffix generator option
+     *
+     * @return string capitalized model name
+     */
+    public static function toModelName(
+        $name,
+        $modelNamePrefix = null,
+        $modelNameSuffix = null
+    ) {
+        if (is_string($name) === false  || empty($name)) {
+            return null;
+        }
+
+        // remove [
+        $name = str_replace(']', '', $name);
+
+        // Note: backslash ("\\") is allowed for e.g. "\\DateTime"
+        $name = preg_replace('/[^\w\\\\]+/', '_', $name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+
+        // remove underscores from start and end
+        $name = trim($name, '_');
+
+        // remove dollar sign
+        $name = str_replace('$', '', $name);
+
+        // model name cannot use reserved keyword
+        if (self::isReservedWord($name)) {
+            $name = 'model_' . $name; // e.g. return => ModelReturn (after camelize)
+        }
+
+        // model name starts with number
+        if (preg_match('/^\d.*/', $name) === 1) {
+            $name = 'model_' . $name; // e.g. 200Response => Model200Response (after camelize)
+        }
+
+        // add prefix and/or suffic only if name does not start wth \ (e.g. \DateTime)
+        if (preg_match('/^\\\\.*/', $name) !== 1) {
+            if (is_string($modelNamePrefix) && !empty($modelNamePrefix)) {
+                $name = $modelNamePrefix . '_' . $name;
+            }
+
+            if (is_string($modelNameSuffix) && !empty($modelNameSuffix)) {
+                $name = $name . '_' . $modelNameSuffix;
+            }
+        }
+
+        // camelize the model name
+        // phone_number => PhoneNumber
+        return self::camelize($name);
+    }
+}
diff --git a/samples/server/petstore/php-slim4/lib/Utils/StringUtilsTrait.php b/samples/server/petstore/php-slim4/lib/Utils/StringUtilsTrait.php
new file mode 100644
index 00000000000..bd0464fa598
--- /dev/null
+++ b/samples/server/petstore/php-slim4/lib/Utils/StringUtilsTrait.php
@@ -0,0 +1,132 @@
+<?php
+
+/**
+ * StringUtilsTrait
+ *
+ * PHP version 7.1
+ *
+ * @package OpenAPIServer
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+
+/**
+ * OpenAPI Petstore
+ *
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ * The version of the OpenAPI document: 1.0.0
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+/**
+ * NOTE: This class is auto generated by the openapi generator program.
+ * https://github.com/openapitools/openapi-generator
+ * Do not edit the class manually.
+ */
+namespace OpenAPIServer\Utils;
+
+/**
+ * StringUtilsTrait Class Doc Comment
+ * This class duplicates functionality of StringUtils.java and AbstractPhpCodegen.java classes.
+ *
+ * @package OpenAPIServer\Utils
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+trait StringUtilsTrait
+{
+    /**
+     * Camelize name (parameter, property, method, etc)
+     * This is recreated method of @link modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/StringUtils.java class.
+     *
+     * @param string $word                 string to be camelize
+     * @param bool   $lowercaseFirstLetter lower case for first letter if set to true
+     *
+     * @return string camelized string
+     */
+    public static function camelize($word, $lowercaseFirstLetter = false)
+    {
+        // Replace all slashes with dots (package separator)
+        $p = '/\/(.?)/';
+        $word = preg_replace($p, '.$1', $word);
+
+        // case out dots
+        $parts = explode('.', $word);
+        $str = '';
+        foreach ($parts as $z) {
+            if (strlen($z) > 0) {
+                $str .= strtoupper(substr($z, 0, 1)) . substr($z, 1);
+            }
+        }
+        $word = $str;
+
+        // Uppercase the class name.
+        $p = '/(\.?)(\w)([^\.]*)$/';
+        $word = preg_replace_callback($p, function ($matches) {
+            $rep = $matches[1] . strtoupper($matches[2]) . $matches[3];
+            $rep = preg_replace('/\$/', '\\\$', $rep);
+            return $rep;
+        }, $word);
+
+        // Remove all underscores (underscore_case to camelCase)
+        $p = '/(_)(.)/';
+        while (preg_match($p, $word, $matches) === 1) {
+            $original = $matches[2][0];
+            $upperCase = strtoupper($original);
+            if ($original === $upperCase) {
+                $word = preg_replace($p, '$2', $word);
+            } else {
+                $word = preg_replace($p, $upperCase, $word);
+            }
+        }
+
+        // Remove all hyphens (hyphen-case to camelCase)
+        $p = '/(-)(.)/';
+        while (preg_match($p, $word, $matches) === 1) {
+            $upperCase = strtoupper($matches[2][0]);
+            $word = preg_replace($p, $upperCase, $word);
+        }
+
+        if ($lowercaseFirstLetter === true && strlen($word) > 0) {
+            $i = 0;
+            $charAt = substr($word, $i, 1);
+            while (
+                $i + 1 < strlen($word)
+                && !(
+                    ($charAt >= 'a' && $charAt <= 'z')
+                    || ($charAt >= 'A' && $charAt <= 'Z')
+                )
+            ) {
+                $i++;
+                $charAt = substr($word, $i, 1);
+            }
+            $i++;
+            $word = strtolower(substr($word, 0, $i)) . substr($word, $i);
+        }
+
+        // remove all underscore
+        $word = str_replace('_', '', $word);
+
+        return $word;
+    }
+
+    /**
+     * Checks whether string is reserved php keyword.
+     * This is recreated method of @link modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java class.
+     *
+     * @param string $word Checked string
+     *
+     * @return bool
+     */
+    public static function isReservedWord($word)
+    {
+        if (is_string($word) === false) {
+            return false;
+        }
+        // __halt_compiler is ommited because class names with underscores not allowed anyway
+        return in_array(
+            strtolower($word),
+            ['abstract', 'and', 'array', 'as', 'break', 'callable', 'case', 'catch', 'class', 'clone', 'const', 'continue', 'declare', 'default', 'die', 'do', 'echo', 'else', 'elseif', 'empty', 'enddeclare', 'endfor', 'endforeach', 'endif', 'endswitch', 'endwhile', 'eval', 'exit', 'extends', 'final', 'for', 'foreach', 'function', 'global', 'goto', 'if', 'implements', 'include', 'include_once', 'instanceof', 'insteadof', 'interface', 'isset', 'list', 'namespace', 'new', 'or', 'print', 'private', 'protected', 'public', 'require', 'require_once', 'return', 'static', 'switch', 'throw', 'trait', 'try', 'unset', 'use', 'var', 'while', 'xor']
+        );
+    }
+}
diff --git a/samples/server/petstore/php-slim4/phpunit.xml.dist b/samples/server/petstore/php-slim4/phpunit.xml.dist
index 50cde966d40..d0904268796 100644
--- a/samples/server/petstore/php-slim4/phpunit.xml.dist
+++ b/samples/server/petstore/php-slim4/phpunit.xml.dist
@@ -20,12 +20,16 @@
         <testsuite name="Mock">
             <directory>./test/Mock</directory>
         </testsuite>
+        <testsuite name="Utils">
+            <directory>./test/Utils</directory>
+        </testsuite>
     </testsuites>
     <filter>
         <whitelist processUncoveredFilesFromWhitelist="true">
             <directory suffix=".php">./lib/Api</directory>
             <directory suffix=".php">./lib/Model</directory>
             <directory suffix=".php">./lib/Mock</directory>
+            <directory suffix=".php">./lib/Utils</directory>
         </whitelist>
     </filter>
     <php>
diff --git a/samples/server/petstore/php-slim4/test/Utils/ModelUtilsTraitTest.php b/samples/server/petstore/php-slim4/test/Utils/ModelUtilsTraitTest.php
new file mode 100644
index 00000000000..9ed05378f2b
--- /dev/null
+++ b/samples/server/petstore/php-slim4/test/Utils/ModelUtilsTraitTest.php
@@ -0,0 +1,102 @@
+<?php
+
+/**
+ * ModelUtilsTraitTest
+ *
+ * PHP version 7.1
+ *
+ * @package OpenAPIServer
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+
+/**
+ * OpenAPI Petstore
+ *
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ * The version of the OpenAPI document: 1.0.0
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+/**
+ * NOTE: This class is auto generated by the openapi generator program.
+ * https://github.com/openapitools/openapi-generator
+ * Do not edit the class manually.
+ */
+namespace OpenAPIServer\Utils;
+
+use OpenAPIServer\Utils\ModelUtilsTrait as ModelUtils;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * ModelUtilsTraitTest Class Doc Comment
+ *
+ * @package OpenAPIServer\Utils
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ * @coversDefaultClass \OpenAPIServer\Utils\ModelUtilsTrait
+ */
+class ModelUtilsTraitTest extends TestCase
+{
+    /**
+     * @covers ::getSimpleRef
+     * @dataProvider provideRefs
+     */
+    public function testGetSimpleRef($ref, $expectedRef)
+    {
+        $this->assertSame($expectedRef, ModelUtils::getSimpleRef($ref));
+    }
+
+    public function provideRefs()
+    {
+        return [
+            'Reference Object OAS 3.0' => [
+                '#/components/schemas/Pet', 'Pet',
+            ],
+            'Reference Object Swagger 2.0' => [
+                '#/definitions/Pet', 'Pet',
+            ],
+            'Underscored classname' => [
+                '#/components/schemas/_foobar_Objects', '_foobar_Objects',
+            ],
+            'Relative Documents With Embedded Schema' => [
+                'definitions.json#/Pet', null,
+            ],
+            'null as argument' => [
+                null, null,
+            ],
+            'number as argument' => [
+                156, null,
+            ],
+        ];
+    }
+
+    /**
+     * @covers ::toModelName
+     * @dataProvider provideModelNames
+     */
+    public function testToModelName($name, $prefix, $suffix, $expectedModel)
+    {
+        $this->assertSame($expectedModel, ModelUtils::toModelName($name, $prefix, $suffix));
+    }
+
+    public function provideModelNames()
+    {
+        return [
+            // fixtures from modules/openapi-generator/src/test/java/org/openapitools/codegen/utils/StringUtilsTest.java
+            ['abcd', null, null, 'Abcd'],
+            ['some-value', null, null, 'SomeValue'],
+            ['some_value', null, null, 'SomeValue'],
+            ['$type', null, null, 'Type'],
+            ['123', null, null, 'Model123'],
+            ['$123', null, null, 'Model123'],
+            ['return', null, null, 'ModelReturn'],
+            ['200Response', null, null, 'Model200Response'],
+            ['abcd', 'SuperModel', null, 'SuperModelAbcd'],
+            ['abcd', null, 'WithEnd', 'AbcdWithEnd'],
+            ['abcd', 'WithStart', 'AndEnd', 'WithStartAbcdAndEnd'],
+            ['_foobar_Objects', null, null, 'FoobarObjects'],
+            [null, null, null, null],
+        ];
+    }
+}
diff --git a/samples/server/petstore/php-slim4/test/Utils/StringUtilsTraitTest.php b/samples/server/petstore/php-slim4/test/Utils/StringUtilsTraitTest.php
new file mode 100644
index 00000000000..d06aa405eeb
--- /dev/null
+++ b/samples/server/petstore/php-slim4/test/Utils/StringUtilsTraitTest.php
@@ -0,0 +1,99 @@
+<?php
+
+/**
+ * StringUtilsTraitTest
+ *
+ * PHP version 7.1
+ *
+ * @package OpenAPIServer
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ */
+
+/**
+ * OpenAPI Petstore
+ *
+ * This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+ * The version of the OpenAPI document: 1.0.0
+ * Generated by: https://github.com/openapitools/openapi-generator.git
+ */
+
+/**
+ * NOTE: This class is auto generated by the openapi generator program.
+ * https://github.com/openapitools/openapi-generator
+ * Do not edit the class manually.
+ */
+namespace OpenAPIServer\Utils;
+
+use OpenAPIServer\Utils\StringUtilsTrait as StringUtils;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * StringUtilsTraitTest Class Doc Comment
+ *
+ * @package OpenAPIServer\Utils
+ * @author  OpenAPI Generator team
+ * @link    https://github.com/openapitools/openapi-generator
+ * @coversDefaultClass \OpenAPIServer\Utils\StringUtilsTrait
+ */
+class StringUtilsTraitTest extends TestCase
+{
+    /**
+     * @covers ::camelize
+     * @dataProvider provideWordsForCamelizeTest
+     */
+    public function testCamelize($word, $lowercaseFirstLetter, $expectedWord)
+    {
+        $this->assertSame($expectedWord, StringUtils::camelize($word, $lowercaseFirstLetter));
+    }
+
+    public function provideWordsForCamelizeTest()
+    {
+        return [
+            // fixtures from modules/openapi-generator/src/test/java/org/openapitools/codegen/utils/StringUtilsTest.java
+            ['openApiServer/model/pet', null, 'OpenApiServerModelPet'],
+            ['abcd', null, 'Abcd'],
+            ['some-value', null, 'SomeValue'],
+            ['some-Value', null, 'SomeValue'],
+            ['some_value', null, 'SomeValue'],
+            ['some_Value', null, 'SomeValue'],
+            ['$type', null, '$Type'],
+
+            ['abcd', true, 'abcd'],
+            ['some-value', true, 'someValue'],
+            ['some_value', true, 'someValue'],
+            ['Abcd', true, 'abcd'],
+            ['$type', true, '$type'],
+
+            ['123', true, '123'],
+            ['$123', true, '$123'],
+        ];
+    }
+
+    /**
+     * @covers ::isReservedWord
+     * @dataProvider provideWordsForIsReservedTest
+     */
+    public function testisReservedWord($word, $expected)
+    {
+        $this->assertSame($expected, StringUtils::isReservedWord($word));
+    }
+
+    public function provideWordsForIsReservedTest()
+    {
+        return [
+            ['return', true],
+            ['switch', true],
+            ['class', true],
+            ['interface', true],
+            ['ABSTRACT', true],
+            ['Trait', true],
+            ['final', true],
+            ['foobar', false],
+            ['DateTime', false],
+            ['Pet', false],
+            [123, false],
+            [null, false],
+        ];
+    }
+}