How to extract a file extension in PHP ?

This is a question you can read everywhere on the web with various answers :

$ext = end(explode('.', $filename));
$ext = substr(strrchr($filename, '.'), 1);
$ext = substr($filename, strrpos($filename, '.') + 1);
$ext = preg_replace('/^.*\.([^.]+)$/D', '$1', $filename);
$exts = split("[/\\.]", $filename);
$n = count($exts)-1;
$ext = $exts[$n];

etc.

However, there is always "the best way" and it should be on stackoverflow.

From stackoverflow e-satis

• pathinfo - http://uk.php.net/manual/en/function.pathinfo.php

  An example...

  $path_info = pathinfo('/foo/bar/baz.bill');
  
  echo $path_info['extension']; // "bill"
  

  vaske : This one is "the best way"
  From Adam Wright

• People from other scripting languages always think theirs is better because they have a built in function to do that and not PHP (I am looking at pythonistas right now :-)).

  In fact, it does exist, but few people know it. Meet pathinfo :

  $ext = pathinfo($filename, PATHINFO_EXTENSION);
  

  This is fast, efficient, reliable and built in. Pathinfo can give you others info, such as canonical path, regarding to the constant you pass to it.

  Enjoy

  J-P : Why didn't you just put the answer in the question!?

  e-satis : Because it's written is the overflow FAQ do it this way.

  Mark Biek : I wish I could vote this up twice. I can't tell you how much code I've been able to replace using pathinfo

  e-satis : So do I. That's why I put it here !
  From e-satis

• E-satis response is the correct way to determine the file extension.

  Alternatively, instead of relying on a files extension, you could use the fileinfo (http://us2.php.net/fileinfo) to determine the files MIME type.

  Here's a simplified example of processing an image uploaded by a user:

  // Code assumes necessary extensions are installed and a successful file upload has already occurred
  
  // Create a FileInfo object
  $finfo = new FileInfo(null, '/path/to/magic/file');
  
  // Determine the MIME type of the uploaded file
  switch ($finfo->file($_FILES['image']['tmp_name'], FILEINFO_MIME) {
      case 'image/jpg':
          $im = imagecreatefromjpeg($_FILES['image']['tmp_name']);
      break;
  
      case 'image/png':
          $im = imagecreatefrompng($_FILES['image']['tmp_name']);
      break;
  
      case 'image/gif':
          $im = imagecreatefromgif($_FILES['image']['tmp_name']);
      break;
  }
  

  From Toxygene