Add syntax highlighting [skip ci]

docs/guide/helper-array.md

@@ -239,20 +239,22 @@ Encoding will use application charset and could be changed via third argument.
 
 ## Merging Arrays <a name="merging-arrays"></a>
 
+```php
   /**
-     * Merges two or more arrays into one recursively.
-     * If each array has an element with the same string key value, the latter
-     * will overwrite the former (different from array_merge_recursive).
-     * Recursive merging will be conducted if both arrays have an element of array
-     * type and are having the same key.
-     * For integer-keyed elements, the elements from the latter array will
-     * be appended to the former array.
-     * @param array $a array to be merged to
-     * @param array $b array to be merged from. You can specify additional
-     * arrays via third argument, fourth argument etc.
-     * @return array the merged array (the original arrays are not changed.)
-     */
+    * Merges two or more arrays into one recursively.
+    * If each array has an element with the same string key value, the latter
+    * will overwrite the former (different from array_merge_recursive).
+    * Recursive merging will be conducted if both arrays have an element of array
+    * type and are having the same key.
+    * For integer-keyed elements, the elements from the latter array will
+    * be appended to the former array.
+    * @param array $a array to be merged to
+    * @param array $b array to be merged from. You can specify additional
+    * arrays via third argument, fourth argument etc.
+    * @return array the merged array (the original arrays are not changed.)
+    */
     public static function merge($a, $b)
+```
 
 
 ## Converting Objects to Arrays <a name="converting-objects-to-arrays"></a>