php obtaining complex file extension like mysql-5.0.1.tar.gz

Question

I've run into a typical problem here. Till now i was doing

strstr($filename,".");

$filename is the file i got from $_FILE i.e uploaded file.It was running fine until i hit a filename of the type i mentioned. Even doing

pathinfo($filename);

gives me

.gz 

I need to see whether it is EXACTLY

.tar.gz

Answer 1

Technically, pathinfo is correct: the one and only extension for that file is .gz. The fact that it has .tar in the name is as coincidental as the fact that it has 5.0.1 in it.

That doesn't make your interest in checking for .tar.gz files invalid, but it does raise the question: what specifically do you want to find?

The most direct solution to your specific question is: first look for the extension (via pathinfo or the strpos function) and then if it happens to be .gz look for the "extension" in the remaining filename (via the same technique).

$parts = pathinfo($filename);
$extension = $parts['extension'];
if ($extension == '.gz') {
    $parts = pathinfo($parts['filename']);
    $extension = $parts['extension'] . $extension;
}

Answer 2

And if you needed to parse 'this.is.a.very.long.file.name.with.lots.of.full.stops' then what part of that is the file extension? Relying on a particular part of a filename to convey semantic, machine readable information about the contents of the file is, at best dangerous.

It's not clear what the problem you are trying is - why do you need to know what the extension is?

C.

Answer 3

The most simple way would be to check for the last 7 characters of the filename - this ensures that every file ends with .tar.gz:

if (substr($filename, -7) == '.tar.gz') {
    // continue
}