PHP natsort ignoring optional prefix

Question

Here a sample code:

<?php
$temp_files = array("_temp15.txt","temp10.txt", "temp1.txt","temp22.txt","_temp2.txt");

natsort($temp_files);
print_r($temp_files);
?>

Actual output:

[4] => _temp2.txt 
[0] => _temp15.txt 
[2] => temp1.txt 
[1] => temp10.txt 
[3] => temp22.txt

Desired output:

[2] => temp1.txt 
[4] => _temp2.txt 
[1] => temp10.txt 
[0] => _temp15.txt 
[3] => temp22.txt

In other words, I want to execute a natural sort ignoring a given (but optional) prefix. In this case the optional prefix is _.

In my use-case scenario the filenames are unique, regardless if the prefix is present or not. I.e. temp1.txt and _temp1.txt are NOT allowed.

The ugly solution I found is:

1. cycle among all items and store the keys with the prefix
2. remove the prefix from the array
3. sort the array
4. restore the prefix using the keys collected at point 1

Is there something better than this brute force approach?

Answer 1

uasort with a custom comparison callback, that uses strnatcmp. Then you can strip off any _ prefixes, before you pass the two values to compare to strnatcmp.

uasort($temp_files, function($a, $b) {
   return strnatcmp(ltrim($a, '_'), ltrim($b, '_')); 
});

Edit: Replaced usort with uasort, to maintain the keys.