compare version using PHP_VERSION_ID

To let opcode caches optimize cached code, the `PHP_VERSION_ID`
constant is used to detect the current PHP version instead of calling
`version_compare()` with `PHP_VERSION`.

Author: xabbuh

Encoder/JsonDecode.php

@@ -92,7 +92,7 @@ public function decode($data, $format, array $context = array())
         $recursionDepth = $context['json_decode_recursion_depth'];
         $options = $context['json_decode_options'];
 
-        if (version_compare(PHP_VERSION, '5.4.0') >= 0) {
+        if (PHP_VERSION_ID >= 50400) {
             $decodedData = json_decode($data, $associative, $recursionDepth, $options);
         } else {
             $decodedData = json_decode($data, $associative, $recursionDepth);