IRsoft - Software and more by Ingmar Runge

PHP: Longest common prefix

This function finds the longest common prefix from a list of strings.

    <?php
     
    // inspired by http://linux.seindal.dk/2005/09/09/longest-common-prefix-in-perl/
     
    function longest_common_prefix(array $arr, $ignore_empty = false)
    {
        $prefix = NULL;
        
        foreach($arr as $s)
        {
            if($ignore_empty && empty($s)) continue;
            
            if(is_null($prefix))
            {
                $prefix = $s;
            }
            else
            {
                while(!empty($prefix) && substr($s, 0, strlen($prefix)) != $prefix)
                {
                    $prefix = substr($prefix, 0, -1);
                }
            }
        }
        
        return $prefix;
    }
     
    ?>

Last edited by Ingmar on Tuesday, April 7th 2009 14:48:17 CEST