MFH: use E_WARNING on recursion and add null to the result to keep it valid

ext/json/json.c

@@ -136,7 +136,8 @@ static void json_encode_array(smart_str *buf, zval **val TSRMLS_DC) {
     }
 
     if (myht && myht->nApplyCount > 1) {
-        php_error_docref(NULL TSRMLS_CC, E_RECOVERABLE_ERROR, "recursion detected");
+        php_error_docref(NULL TSRMLS_CC, E_WARNING, "recursion detected");
+        smart_str_appendl(buf, "null", 4);
         return;
     }
 

ext/json/tests/003.phpt

@@ -25,4 +25,6 @@ array(1) {
   }
 }
 
-Catchable fatal error: json_encode(): recursion detected in %s on line %d
+Warning: json_encode(): recursion detected in %s on line %d
+string(8) "[[null]]"
+Done

ext/json/tests/004.phpt

@@ -22,4 +22,6 @@ object(stdClass)#%d (1) {
   }
 }
 
-Catchable fatal error: json_encode(): recursion detected in %s on line %d
+Warning: json_encode(): recursion detected in %s on line %d
+string(22) "{"prop":{"prop":null}}"
+Done

ext/json/tests/005.phpt

@@ -22,4 +22,6 @@ array(1) {
   }
 }
 
-Catchable fatal error: json_encode(): recursion detected in %s on line %d
+Warning: json_encode(): recursion detected in %s on line %d
+string(8) "[[null]]"
+Done