diff --git a/modules/openapi-generator/src/main/resources/php-nextgen/model_generic.mustache b/modules/openapi-generator/src/main/resources/php-nextgen/model_generic.mustache
index 0a199d959f74..109c5ea42933 100644
--- a/modules/openapi-generator/src/main/resources/php-nextgen/model_generic.mustache
+++ b/modules/openapi-generator/src/main/resources/php-nextgen/model_generic.mustache
@@ -446,7 +446,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
         }
         {{/minimum}}
         {{#pattern}}
-        if ({{#isNullable}}!is_null(${{name}}) && {{/isNullable}}(!preg_match("{{{pattern}}}", ${{name}}))) {
+        if ({{#isNullable}}!is_null(${{name}}) && {{/isNullable}}(!preg_match("{{{pattern}}}", ObjectSerializer::toString(${{name}})))) {
             throw new InvalidArgumentException("invalid value for \${{name}} when calling {{classname}}.{{operationId}}, must conform to the pattern {{{pattern}}}.");
         }
         {{/pattern}}
diff --git a/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/FormatTest.php b/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/FormatTest.php
index 83f78ff27a84..1deda3bbc717 100644
--- a/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/FormatTest.php
+++ b/samples/client/petstore/php-nextgen/OpenAPIClient-php/src/Model/FormatTest.php
@@ -716,7 +716,7 @@ public function setString(?string $string): static
             throw new InvalidArgumentException('non-nullable string cannot be null');
         }
 
-        if ((!preg_match("/[a-z]/i", $string))) {
+        if ((!preg_match("/[a-z]/i", ObjectSerializer::toString($string)))) {
             throw new InvalidArgumentException("invalid value for \$string when calling FormatTest., must conform to the pattern /[a-z]/i.");
         }
 
@@ -917,7 +917,7 @@ public function setPatternWithDigits(?string $pattern_with_digits): static
             throw new InvalidArgumentException('non-nullable pattern_with_digits cannot be null');
         }
 
-        if ((!preg_match("/^\\d{10}$/", $pattern_with_digits))) {
+        if ((!preg_match("/^\\d{10}$/", ObjectSerializer::toString($pattern_with_digits)))) {
             throw new InvalidArgumentException("invalid value for \$pattern_with_digits when calling FormatTest., must conform to the pattern /^\\d{10}$/.");
         }
 
@@ -949,7 +949,7 @@ public function setPatternWithDigitsAndDelimiter(?string $pattern_with_digits_an
             throw new InvalidArgumentException('non-nullable pattern_with_digits_and_delimiter cannot be null');
         }
 
-        if ((!preg_match("/^image_\\d{1,3}$/i", $pattern_with_digits_and_delimiter))) {
+        if ((!preg_match("/^image_\\d{1,3}$/i", ObjectSerializer::toString($pattern_with_digits_and_delimiter)))) {
             throw new InvalidArgumentException("invalid value for \$pattern_with_digits_and_delimiter when calling FormatTest., must conform to the pattern /^image_\\d{1,3}$/i.");
         }