Determining a Local File's Mime Type (Content-type) With PHP

Question

I am trying to determine a file's mime type. I've tried a few methods, but haven't come up with anything that gives consistent output. I've tried $mime = mime_content_type($file) and $mime = exec('file -bi ' . $file). I am serving up images, CSS, and JavaScript.

Example mime_content_type() output:

jquery.min.js - text/plain
editor.js - text/plain
admin.css - text/plain
controls.css - application/x-troff
logo.png - text/plain

Example exec(...) output:

jquery.min.js - text/plain; charset=us-ascii
editor.js - text/x-c++; charset=us-ascii
admin.css - text/x-c; charset=us-ascii
controls.css - text/x-c; charset=us-ascii
logo.png - image/png

As can be seen here, the results are all over the place.

My PHP version is 5.2.6

SOLUTION (thanks to Jacob)

$mimetypes = array(
    'gif' => 'image/gif',
    'png' => 'image/png',
    'jpg' => 'image/jpg',
    'css' => 'text/css',
    'js' => 'text/javascript',
);
$path_parts = pathinfo($file);
if (array_key_exists($path_parts['extension'], $mimetypes)) {
    $mime = $mimetypes[$path_parts['extension']];
} else {
    $mime = 'application/octet-stream';
}

You said that you were using 5.2.6, how then are you using fileinfo? — Jacob Relkin
– Jacob Relkin, Commented Mar 16, 2010 at 20:00
pathinfo() has been around since PHP 4.0.3 - us.php.net/pathinfo — Sonny
– Sonny, Commented Mar 16, 2010 at 20:21
upvoted for adding solution, that said, the solution provided is inherently insecure as it only checks file extensions and should not be used on uploaded files to check validity. — buggedcom
– buggedcom, Commented Aug 25, 2010 at 11:23
@buggedcom - I agree. In my case, the files are managed by us, so this solution is acceptable. I couldn't find a secure solution that worked. I'd be willing to award an accepted answer for a secure solution that works. — Sonny
– Sonny, Commented Aug 27, 2010 at 14:08

Jacob Relkin · Accepted Answer · 2014-01-15 19:53:48Z

4

The Fileinfo extension will do the job, if you're on >= 5.30

You should try to avoid having to execute commands
mime_content_type is deprecated in PHP 5.30

If unfortunately you are on < 5.30, then I would probably just write it myself, it's a lot more reliable than what you're getting from the above functions/commands.

Here's an example:

<?php
$filename = 'FILENAME HERE';
$mimetypes = array('png' => 'image/png', 'jpg' => 'image/jpg', 'css' => 'text/css',
    'js' => 'application/x-javascript'
    // any other extensions that you may be serving      
);

$ext = strtolower(substr($filename, strrpos($filename, '.') + 1, strlen($filename)));
if(array_key_exists($ext, $mimetypes)) {
    $mime = $mimetypes[$ext];
} else {
    echo 'mime type not found';
}

?>

edited Jan 15, 2014 at 19:53

answered Mar 16, 2010 at 15:08

Jacob Relkin

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2 Comments

Sonny Over a year ago

The Fileinfo is PHP >= 5.3.0. I am on 5.2.6. I just updated my post to reflect this.

Sonny Over a year ago

Using your solution, but you should change in_array() to array_key_exists() and reverse the arguments.

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