diff --git a/modules/openapi-generator/src/main/resources/php-nextgen/ObjectSerializer.mustache b/modules/openapi-generator/src/main/resources/php-nextgen/ObjectSerializer.mustache
index aec98f8b9e8..9c57c887441 100644
--- a/modules/openapi-generator/src/main/resources/php-nextgen/ObjectSerializer.mustache
+++ b/modules/openapi-generator/src/main/resources/php-nextgen/ObjectSerializer.mustache
@@ -188,6 +188,9 @@ class ObjectSerializer
             # For boolean values, '' is considered empty
             'bool','boolean' => !in_array($value, [false, 0], true),
 
+            # For string values, '' is considered empty.
+            'string' => $value === '',
+
             # For all the other types, any value at this point can be considered empty.
             default => true
         };
diff --git a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
index a126b346ebc..00aeea6cbcc 100644
--- a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
+++ b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
@@ -185,6 +185,10 @@ class ObjectSerializer
             case 'boolean':
                 return !in_array($value, [false, 0], true);
 
+            # For string values, '' is considered empty.
+            case 'string':
+                return $value === '';
+
             # For all the other types, any value at this point can be considered empty.
             default:
                 return true;
diff --git a/samples/client/echo_api/php-nextgen-streaming/src/ObjectSerializer.php b/samples/client/echo_api/php-nextgen-streaming/src/ObjectSerializer.php
index 3dfd7c05f58..e75e7b623e0 100644
--- a/samples/client/echo_api/php-nextgen-streaming/src/ObjectSerializer.php
+++ b/samples/client/echo_api/php-nextgen-streaming/src/ObjectSerializer.php
@@ -198,6 +198,9 @@ class ObjectSerializer
             # For boolean values, '' is considered empty
             'bool','boolean' => !in_array($value, [false, 0], true),
 
+            # For string values, '' is considered empty.
+            'string' => $value === '',
+
             # For all the other types, any value at this point can be considered empty.
             default => true
         };
diff --git a/samples/client/echo_api/php-nextgen/src/ObjectSerializer.php b/samples/client/echo_api/php-nextgen/src/ObjectSerializer.php
index 3dfd7c05f58..e75e7b623e0 100644
--- a/samples/client/echo_api/php-nextgen/src/ObjectSerializer.php
+++ b/samples/client/echo_api/php-nextgen/src/ObjectSerializer.php
@@ -198,6 +198,9 @@ class ObjectSerializer
             # For boolean values, '' is considered empty
             'bool','boolean' => !in_array($value, [false, 0], true),
 
+            # For string values, '' is considered empty.
+            'string' => $value === '',
+
             # For all the other types, any value at this point can be considered empty.
             default => true
         };
diff --git a/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/ObjectSerializer.php b/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/ObjectSerializer.php
index 9e46385b4c7..ad81c50c69d 100644
--- a/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/ObjectSerializer.php
+++ b/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/ObjectSerializer.php
@@ -197,6 +197,9 @@ class ObjectSerializer
             # For boolean values, '' is considered empty
             'bool','boolean' => !in_array($value, [false, 0], true),
 
+            # For string values, '' is considered empty.
+            'string' => $value === '',
+
             # For all the other types, any value at this point can be considered empty.
             default => true
         };
diff --git a/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php b/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
index a02f072f66b..03f89f0bcad 100644
--- a/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
+++ b/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
@@ -194,6 +194,10 @@ class ObjectSerializer
             case 'boolean':
                 return !in_array($value, [false, 0], true);
 
+            # For string values, '' is considered empty.
+            case 'string':
+                return $value === '';
+
             # For all the other types, any value at this point can be considered empty.
             default:
                 return true;
diff --git a/samples/client/petstore/php/OpenAPIClient-php/tests/ObjectSerializerTest.php b/samples/client/petstore/php/OpenAPIClient-php/tests/ObjectSerializerTest.php
index 4ca73b37565..dc71cd108b8 100644
--- a/samples/client/petstore/php/OpenAPIClient-php/tests/ObjectSerializerTest.php
+++ b/samples/client/petstore/php/OpenAPIClient-php/tests/ObjectSerializerTest.php
@@ -430,6 +430,9 @@ class ObjectSerializerTest extends TestCase
             'form 0 bool, explode on, required false' => [
                 0, 'field', 'bool', 'form', true, false, 'field=0',
             ],
+            'form string "0", explode on, required true' => [
+                '0', 'field', 'string', 'form', true, true, 'field=0',
+            ],
         ];
     }
 
diff --git a/samples/client/petstore/php/psr-18/lib/ObjectSerializer.php b/samples/client/petstore/php/psr-18/lib/ObjectSerializer.php
index a02f072f66b..03f89f0bcad 100644
--- a/samples/client/petstore/php/psr-18/lib/ObjectSerializer.php
+++ b/samples/client/petstore/php/psr-18/lib/ObjectSerializer.php
@@ -194,6 +194,10 @@ class ObjectSerializer
             case 'boolean':
                 return !in_array($value, [false, 0], true);
 
+            # For string values, '' is considered empty.
+            case 'string':
+                return $value === '';
+
             # For all the other types, any value at this point can be considered empty.
             default:
                 return true;