title: Time Complexity of array_filter in PHP
body: <p>Assuming that the callback function(s) that I am using have a time complexity of O(1), what is the running time of the <a href="http://php.net/manual/en/function.array-filter.php" rel="nofollow">array_filter function</a> in PHP and is there somewhere I can find the implementation of the array_filter function?</p>
  
  <p>Thanks</p>