Fix bug when variables key doesn't exist (#7429)

Author: ybelenko

modules/openapi-generator/src/main/resources/php/Configuration.mustache

@@ -482,7 +482,7 @@ class Configuration
         $url = $host["url"];
 
         // go through variable and assign a value
-        foreach ($host["variables"] as $name => $variable) {
+        foreach ($host["variables"] ?? [] as $name => $variable) {
             if (array_key_exists($name, $variables)) { // check to see if it's in the variables provided by the user
                 if (in_array($variables[$name], $variable["enum_values"], true)) { // check to see if the value is in the enum
                     $url = str_replace("{".$name."}", $variables[$name], $url);

samples/client/petstore/php/OpenAPIClient-php/lib/Configuration.php

@@ -499,7 +499,7 @@ public function getHostFromSettings($index, $variables = null)
         $url = $host["url"];
 
         // go through variable and assign a value
-        foreach ($host["variables"] as $name => $variable) {
+        foreach ($host["variables"] ?? [] as $name => $variable) {
             if (array_key_exists($name, $variables)) { // check to see if it's in the variables provided by the user
                 if (in_array($variables[$name], $variable["enum_values"], true)) { // check to see if the value is in the enum
                     $url = str_replace("{".$name."}", $variables[$name], $url);