diff --git a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
index 3ab026909ec..526665f2717 100644
--- a/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
+++ b/modules/openapi-generator/src/main/resources/php/ObjectSerializer.mustache
@@ -165,8 +165,9 @@ class ObjectSerializer
      * Take value and turn it into a string suitable for inclusion in
      * the parameter. If it's a string, pass through unchanged
      * If it's a datetime object, format it in ISO8601
+     * If it's a boolean, convert it to "true" or "false".
      *
-     * @param string|\DateTime $value the value of the parameter
+     * @param string|bool|\DateTime $value the value of the parameter
      *
      * @return string the header string
      */
@@ -174,6 +175,8 @@ class ObjectSerializer
     {
         if ($value instanceof \DateTime) { // datetime in ISO8601 format
             return $value->format(\DateTime::ATOM);
+        } else if (is_bool($value)) {
+            return $value ? 'true' : 'false';
         } else {
             return $value;
         }
diff --git a/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php b/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
index d8bff1321ac..e62da54b988 100644
--- a/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
+++ b/samples/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
@@ -175,8 +175,9 @@ class ObjectSerializer
      * Take value and turn it into a string suitable for inclusion in
      * the parameter. If it's a string, pass through unchanged
      * If it's a datetime object, format it in ISO8601
+     * If it's a boolean, convert it to "true" or "false".
      *
-     * @param string|\DateTime $value the value of the parameter
+     * @param string|bool|\DateTime $value the value of the parameter
      *
      * @return string the header string
      */
@@ -184,6 +185,8 @@ class ObjectSerializer
     {
         if ($value instanceof \DateTime) { // datetime in ISO8601 format
             return $value->format(\DateTime::ATOM);
+        } else if (is_bool($value)) {
+            return $value ? 'true' : 'false';
         } else {
             return $value;
         }
diff --git a/samples/openapi3/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php b/samples/openapi3/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
index d8bff1321ac..e62da54b988 100644
--- a/samples/openapi3/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
+++ b/samples/openapi3/client/petstore/php/OpenAPIClient-php/lib/ObjectSerializer.php
@@ -175,8 +175,9 @@ class ObjectSerializer
      * Take value and turn it into a string suitable for inclusion in
      * the parameter. If it's a string, pass through unchanged
      * If it's a datetime object, format it in ISO8601
+     * If it's a boolean, convert it to "true" or "false".
      *
-     * @param string|\DateTime $value the value of the parameter
+     * @param string|bool|\DateTime $value the value of the parameter
      *
      * @return string the header string
      */
@@ -184,6 +185,8 @@ class ObjectSerializer
     {
         if ($value instanceof \DateTime) { // datetime in ISO8601 format
             return $value->format(\DateTime::ATOM);
+        } else if (is_bool($value)) {
+            return $value ? 'true' : 'false';
         } else {
             return $value;
         }