Getting File's Extension with Regular Expression

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Getting file extension is not as easy as it looks. This is because there is no strict format for file extensions. Consider the following file names:

test.jpg
another image.jpeg
PHP Tutorial from Nashruddin.pdf
unusual.name.for.a.file.extension
my favorite, music.mp3


You cannot get the extension with substr($filename, -n), for example.To obtain the extension from filenames above, you have to use regular expression. See the following example.

<?php
$filenames = array(
        'test.jpg',
        'longfilename.html',
        'PHP Tutorial from Nashruddin.pdf',
        'unusual.name.for.a.file.extension',
        'another, weird, file.jpeg',
        'my favorite song.mp3'
    );

foreach ($filenames as $filename) {
    preg_match("/\.([^\.]+)$/", $filename, $matches);    
    print $matches[1] . '<br>';
}

/* will print:
jpg
html
pdf
extension
jpeg
mp3 */
?>

Keywords: regular expression, preg_match, file extension, php

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