Improve performance of settings save by not querying the DB if submitted value is the same

include/Core/PConfig.php

@@ -123,6 +123,10 @@ class PConfig {
 
 		global $a;
 
+        if (self::get($uid, $family, $key) === $value) {
+            return true;
+        }
+
 		// manage array value
 		$dbvalue = (is_array($value)?serialize($value):$value);