Rocksolid function for get extension of file by it mime type

getExtByMimeType.php

<?php
    function getExtByMimeType($mime) {

        $known_files = array(
            '/etc/mime.types',
            '/etc/httpd/mime.types',
            'C:\Program Files\Apache Group\Apache\conf\mime.types'
        ); /* If mime type file of your system not listed here, please add it path here */

        $extensionFile = null;

        for ($i = 0; $i<count($known_files); $i++) {
            if (file_exists($known_files[$i])) {
                $extensionFile = file($known_files[$i]);
                break;
            } 
        }

        if ($extensionFile === null) {
            return false;
        }

        foreach($extensionFile as $line) {
            if ($line[0] != '#') {
                $parts = explode("\t",$line);
                if (strtolower($parts[0])==strtolower($mime)) {
                    $extensions = strtolower($parts[count($parts)-1]); 
                    list($extension, ) = explode(' ', $extensions, 2);
                    return $extension;
                }
            }
        }
        return false;
    }