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 23210e174e62..6d6b6ed44138 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
@@ -274,8 +274,8 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
 
         {{#vars}}
         {{#required}}
-        if ($this->container['{{name}}'] === null) {
-            $invalidProperties[] = "'{{name}}' can't be null";
+        if ($this->container['{{name}}'] === null{{#isNullable}} && !$this->isNullableSetToNull('{{name}}'){{/isNullable}}) {
+            $invalidProperties[] = "'{{name}}' {{^isNullable}}can't be null"{{/isNullable}}{{#isNullable}}is required"{{/isNullable}};
         }
         {{/required}}
         {{#isEnum}}
@@ -293,43 +293,43 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
         {{/isEnum}}
         {{#hasValidation}}
         {{#maxLength}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}(mb_strlen($this->container['{{name}}']) > {{maxLength}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}(mb_strlen($this->container['{{name}}']) > {{maxLength}})) {
             $invalidProperties[] = "invalid value for '{{name}}', the character length must be smaller than or equal to {{{maxLength}}}.";
         }
 
         {{/maxLength}}
         {{#minLength}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}(mb_strlen($this->container['{{name}}']) < {{minLength}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}(mb_strlen($this->container['{{name}}']) < {{minLength}})) {
             $invalidProperties[] = "invalid value for '{{name}}', the character length must be bigger than or equal to {{{minLength}}}.";
         }
 
         {{/minLength}}
         {{#maximum}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}($this->container['{{name}}'] >{{#exclusiveMaximum}}={{/exclusiveMaximum}} {{maximum}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}($this->container['{{name}}'] >{{#exclusiveMaximum}}={{/exclusiveMaximum}} {{maximum}})) {
             $invalidProperties[] = "invalid value for '{{name}}', must be smaller than {{^exclusiveMaximum}}or equal to {{/exclusiveMaximum}}{{maximum}}.";
         }
 
         {{/maximum}}
         {{#minimum}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}($this->container['{{name}}'] <{{#exclusiveMinimum}}={{/exclusiveMinimum}} {{minimum}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}($this->container['{{name}}'] <{{#exclusiveMinimum}}={{/exclusiveMinimum}} {{minimum}})) {
             $invalidProperties[] = "invalid value for '{{name}}', must be bigger than {{^exclusiveMinimum}}or equal to {{/exclusiveMinimum}}{{minimum}}.";
         }
 
         {{/minimum}}
         {{#pattern}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}!preg_match("{{{pattern}}}", $this->container['{{name}}'])) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}!preg_match("{{{pattern}}}", $this->container['{{name}}'])) {
             $invalidProperties[] = "invalid value for '{{name}}', must be conform to the pattern {{{pattern}}}.";
         }
 
         {{/pattern}}
         {{#maxItems}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}(count($this->container['{{name}}']) > {{maxItems}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}(count($this->container['{{name}}']) > {{maxItems}})) {
             $invalidProperties[] = "invalid value for '{{name}}', number of items must be less than or equal to {{{maxItems}}}.";
         }
 
         {{/maxItems}}
         {{#minItems}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}(count($this->container['{{name}}']) < {{minItems}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}(count($this->container['{{name}}']) < {{minItems}})) {
             $invalidProperties[] = "invalid value for '{{name}}', number of items must be greater than or equal to {{{minItems}}}.";
         }
 
diff --git a/modules/openapi-generator/src/main/resources/php/model_generic.mustache b/modules/openapi-generator/src/main/resources/php/model_generic.mustache
index 94fb895fceb5..bd8ac810a0fa 100644
--- a/modules/openapi-generator/src/main/resources/php/model_generic.mustache
+++ b/modules/openapi-generator/src/main/resources/php/model_generic.mustache
@@ -285,7 +285,7 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
         {{#vars}}
         {{#required}}
         if ($this->container['{{name}}'] === null{{#isNullable}} && !$this->isNullableSetToNull('{{name}}'){{/isNullable}}) {
-            $invalidProperties[] = "'{{name}}' can't be null";
+            $invalidProperties[] = "'{{name}}' {{^isNullable}}can't be null"{{/isNullable}}{{#isNullable}}is required"{{/isNullable}};
         }
         {{/required}}
         {{#isEnum}}
@@ -303,37 +303,37 @@ class {{classname}} {{#parentSchema}}extends {{{parent}}}{{/parentSchema}}{{^par
         {{/isEnum}}
         {{#hasValidation}}
         {{#maxLength}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}(mb_strlen($this->container['{{name}}']) > {{maxLength}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}(mb_strlen($this->container['{{name}}']) > {{maxLength}})) {
             $invalidProperties[] = "invalid value for '{{name}}', the character length must be smaller than or equal to {{{maxLength}}}.";
         }
 
         {{/maxLength}}
         {{#minLength}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}(mb_strlen($this->container['{{name}}']) < {{minLength}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}(mb_strlen($this->container['{{name}}']) < {{minLength}})) {
             $invalidProperties[] = "invalid value for '{{name}}', the character length must be bigger than or equal to {{{minLength}}}.";
         }
 
         {{/minLength}}
         {{#maximum}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}($this->container['{{name}}'] >{{#exclusiveMaximum}}={{/exclusiveMaximum}} {{maximum}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}($this->container['{{name}}'] >{{#exclusiveMaximum}}={{/exclusiveMaximum}} {{maximum}})) {
             $invalidProperties[] = "invalid value for '{{name}}', must be smaller than {{^exclusiveMaximum}}or equal to {{/exclusiveMaximum}}{{maximum}}.";
         }
 
         {{/maximum}}
         {{#minimum}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}($this->container['{{name}}'] <{{#exclusiveMinimum}}={{/exclusiveMinimum}} {{minimum}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}($this->container['{{name}}'] <{{#exclusiveMinimum}}={{/exclusiveMinimum}} {{minimum}})) {
             $invalidProperties[] = "invalid value for '{{name}}', must be bigger than {{^exclusiveMinimum}}or equal to {{/exclusiveMinimum}}{{minimum}}.";
         }
 
         {{/minimum}}
         {{#pattern}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}!preg_match("{{{pattern}}}", $this->container['{{name}}'])) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}!preg_match("{{{pattern}}}", $this->container['{{name}}'])) {
             $invalidProperties[] = "invalid value for '{{name}}', must be conform to the pattern {{{pattern}}}.";
         }
 
         {{/pattern}}
         {{#maxItems}}
-        if ({{^required}}!is_null($this->container['{{name}}']) && {{/required}}(count($this->container['{{name}}']) > {{maxItems}})) {
+        if ({{#notRequiredOrIsNullable}}!is_null($this->container['{{name}}']) && {{/notRequiredOrIsNullable}}(count($this->container['{{name}}']) > {{maxItems}})) {
             $invalidProperties[] = "invalid value for '{{name}}', number of items must be less than or equal to {{{maxItems}}}.";
         }