[php Symfony] fix return type for non json/xml api

This fixes the generated returned type of controller methods for
endpoint with a response declared like

    content:
      text/plain:
        schema:
          type: <boolean|string|integer|number>

or for

    content:
      image/png:
        schema:
          type: string
          format: binary

Without this commit the generated method *had to* return a value that
matched "array|object|null", which does not work in this case.
This commit makes it possible to return the proper type.

Author: gturri

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSymfonyServerCodegen.java

@@ -417,10 +417,16 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
                 op.vendorExtensions.put("x-comment-type", "void");
             }
             // Create a variable to add typing for return value of interface
-            if (op.returnType != null) {
+            if (op.returnType == null) {
+                op.vendorExtensions.put("x-return-type", "void");
+            } else if (op.isArray || op.isMap || isApplicationJsonOrApplicationXml(op)
+                    || !op.returnTypeIsPrimitive // it could make sense to remove it, but it would break retro-compatibility
+            ) {
                 op.vendorExtensions.put("x-return-type", "array|object|null");
+            } else if ("binary".equals(op.returnProperty.dataFormat)) {
+                op.vendorExtensions.put("x-return-type", "mixed");
             } else {
-                op.vendorExtensions.put("x-return-type", "void");
+                op.vendorExtensions.put("x-return-type", op.returnType);
             }
 
             // Add operation's authentication methods to whole interface
@@ -438,6 +444,18 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         return objs;
     }
 
+    private boolean isApplicationJsonOrApplicationXml(CodegenOperation op) {
+       if (op.produces != null) {
+           for(Map<String, String> produce : op.produces) {
+               String mediaType = produce.get("mediaType");
+               if (isJsonMimeType(mediaType) || isXmlMimeType(mediaType)) {
+                  return true;
+               }
+           }
+       }
+       return false;
+    }
+
     @Override
     public ModelsMap postProcessModels(ModelsMap objs) {
         objs = super.postProcessModels(objs);