Over time, I’ve seen a wide range of scripts which for one reason or another have had the need to grab the extension from a file name or path (E.g. “gif” from “mypic.gif”). Oftentimes the solution tends to fall back on what the task appears to need: string manipulation. Though, as you’ll see, this may not be the best approach to take.
To make things a little clearer for people who can visualise code more easily than paragraphs of text, here are a few examples of what I’ve seen used in the past. The samples are mostly compacted onto a single line but if you’re not comfortable with multiple things happening in one line, feel free to expand them into multiple steps. In all cases, $ext ends up being “gif” .
// 1. The "explode/end" approach
$ext = end(explode('.', $filename));
// 2. The "strrchr" approach
$ext = substr(strrchr($filename, '.'), 1);
// 3. The "strrpos" approach
$ext = substr($filename, strrpos($filename, '.') + 1);
// 4. The "preg_replace" approach
$ext = preg_replace('/^.*\.([^.]+)$/D', '$1', $filename);
// 5. The "never use this" approach
// From: http://php.about.com/od/finishedphp1/qt/file_ext_PHP.htm
$exts = split("[/\\.]", $filename);
$n = count($exts)-1;
$ext = $exts[$n];
Forgetting approach number 5 (the “never use this” approach!), they seem fairly reasonable ways of parsing the $filename string and grabbing the extension. So much so that those approaches can be found dotted around the interweb when people ask the question “How to get the file extension in PHP?”
Speed, baby, speed!
Because these are commonly used snippets of code, I decided to pitch them against each other and find out which was the most efficient–by that I simply mean the fastest processing–method just to satisfy my curiosity. The exact details of how they were tested I don’t plan to go into in this post, but here is what I found. On order of fastest to slowest were:
- strrchr
- closely followed by strrpos
- then preg_replace
- with explode/end coming in almost twice as slow as the str* methods
Great, so the idea is to use the $ext = substr(strrchr($filename, '.'), 1); approach from now on? Hold on there sonny boy, not so fast! There is another contender which has not been considered yet (though some of you would have been screaming his name from the start). Time to introduce the pathinfo function.
“Hello”, says pathinfo.
Pathinfo does a number of things, depending on what we ask of it, but put simply it returns (path) information about a filepath. Full details can be found on the handy dandy pathinfo page in the PHP manual. Explore the PHP manual page when you get time, but for the purpose of this blog post I’ll hone in to one specific use of the function: getting the file extension. In order to do that, we simply call the function passing along the full filename and a ‘flag’ (a constant which dictates the behaviour of the function) asking for the extension only.
That’s all there is to it! In my opinion, this approach ‘reads’ much more easily than the mess of nested function calls and playing around with string positions, regular expressions, etc.. It is concise and to the point: call pathinfo and only give me back the extension. Simple.
Now for the icing on the cake. When pitched against the other methods detailed above, this call to pathinfo beats all of the others into submission. At least in my testing, it is the fastest method of all (though in random hiccups strrchr does win in around 1% of tests) being on average 1/10th faster than even the strrchr approach.
Summary, or “the bit lazy people should read”
So, to cut a long blog post short, the method that I’ll be using to grab the file extension is simply:
What do you currently use? Have you had any problems using pathinfo, any particular quirks or annoyances?
74 Comments on PHP Get File Extension.
I used the explode() method which was really clean to me. explode() never annoyed me but it was a bit longer since you need to work on the array to print out the extension. (without die, I suppose).
pathinfo() is really easy as compared to all the other contenders but proper profiling still needs to be done to find the fastest contender in terms of speed. I don’t really care about those 0.00001ms of speed but some do..
I know that someone are very, very interested in scraping away those thousands of milliseconds from their scripts — to a degree it also interests me in a “hmm, lets see what we can do” way rather than a necessity for each and every line of code I ever create.
Personally, I think that
pathinfo(..., PATHINFO_EXTENSION)is by far the easiest code snippet to read and understand quickly what is going on, compared to the other alternatives posted here.Hey. Just dropping a note of appreciation. Nice when someone publishes something that is simple and direct as to the best practice, given the myriad of options available to you in PHP.
Thanks!
If you are making a file upload script, it is crucial that you use the pathinfo method to finding the true file extension. Because it is possible to fake out php by just renaming the file’s extension. Then when you upload it, if you use explode / strchr method, it will give you the wrong extension.
I’m not sure how providing a file extension which does not match the file content will “fake out” PHP but I do know that whichever of the methods listed above is used, they each produce the same result. If explode / strchr methods give the “wrong” extension, so will pathinfo.
Oh sorry, I was thinking of something else: http://www.jellyandcustard.com/2006/01/19/php-mime-types-and-fileinfo/
But that’s only really important for file uploads, and I guess you were mainly talking about files that were already on the server. Myyy badd.
if you can live with the dot:
strrchr($name,’.')
will return “.php”
That’s about ~2x faster than pathinfo()
Thank you.
Nice and direct.
Beautifully explained. Thanks!
This is a great post, with useful, practical information. Hat’s off to you, sir.
what about
$filename = ‘my.pic.gif’;
Robin,
pathinfo('my.pic.gif', PATHINFO_EXTENSION)would returngifas expected.Thanks for this
There are so many functions in PHP, and I have now discovered a new one 
And what about this:
$fileinfo = “file.tar.gz”;
Would it return the proper tar.gz or just the gz?
Any way to easy do this or do we have to use the explode and check for every filetype? :/
Cheers,
Thanks for the comment Josso. In that case
gz
would be returned as the file extension (which is fine if you see it as a gzipped tar file, and not a “tar gzip” file). It would be easy enough to look for the
tarif you needed to for whatever reason.Josso:
A file named file.tar.gz is a gzip file, so ‘gz’ is the proper extension. If you gunzip it, you are left with a tarball with a ‘tar’ extension. This is all by design. An alternate extension for a gzipped tarball is .tgz, however it’s more technically valid to have .tar.gz. It does matter when you run into an instance where you want to gunzip without extracting the tarball.
Ummm, NO! Do NOT use explode, strchr, substr etc. to parse filenames like this. You will end up with bugs and potential security problems. Why? Well, think about all the different permutations of filenames that can cause problems. This is especially true of user-input strings (like for file uploads, etc.). Use the pathinfo() function.
Please update your article to reflect this so the monkeys of the world will stop using strchr in their code to parse paths. Thanks.
Would the monkey please take care to actually read the article in its entirety? The advice in the article is indeed to use the pathinfo function and there’s even a “bit lazy people should read” which summarises the post in under 30 words, but thanks for your concern.
Thank you.
Nice and direct.
Great article specifically for the speed testing of the different options listed. Came in handy for a directory listing script I’m working on. Thanks!
[...] get file extension comparison [...]
i think that the explode method is not a reliable one.B’coz try uploading a file named filename.gif.php, the explode method will return the extension as .gif and it ignores the .php part. its a potentional security flow as any one can uplaod the php file and execute it.
So i would recommend using the pathinfo function.
Absolutely, that’s the entire point of this article. Thanks for commenting.
Great accurate article. Thanks for condensing the functions into one lines as well, I always try to make my code as concise as possible. Thanks.
Thanks Eric. I too like concise code so long as it’s concise and readable; if the code is just mushed together and obfuscated for the sake of keeping it small, then that’s no so cool.
thank you very much
helpful and direct..
keep it up!
Thank you.
You need to organize this article better… someone could read the first 2 paragraphs, decide that strrchr never realizing pathinfo is proper!
pathinfo should be mentioned from the very beginning and listed with all the other options, and it would make way more sense.
Marcus, the particular structure was chosen as a story moving from the bad to the good. For people that cannot be bothered to read and digest the whole article (it’s hardly a monster, nor complicated!) then I cannot be bothered to try and teach them something.
For those who will actually read an article, the information is all there. I did go to the trouble of adding “the bit lazy people should read” for those who like to scan headings and still numerous people have taken the time to comment that I should have recommended
pathinfo.Hi Peter,
Many thanks for this!
Please ignore the people who didn’t bother to read the whole article and give us more of the same.
Simple, yet thorough, explanations of PHP best practices are severely lacking on the internet.
Your RSS feed has just gotten another subscriber…
Thanks Mark, if you have any suggestions on topics to cover they would be more then welcomed.
P.S. Welcome to the tiny, yet super-special, few who subscribe to here.
Thanks dude!!! I was trying just like a monkey and getting nothing… A lot of scripts on internet with difficult approach. Your solution came from heaven!!!
[Ed. Code snippet not using
pathinfo()removed.]thank you. this helps me a lot.
Thanks. Very nice selection of options, and the best part — you did a test to find the fastest for us
Be careful using the first example.
split()is deprecated in PHP 5.3.Nice blog post though. Thanks!
Nice code bro. Im looking for this,
all methods fail if path has query or hash:
$filename = “mypic.gif?see=me#now”;
@staima: Just like any other function, if you put rubbish in then you’ll (probably) get rubbish out; File paths don’t have query strings.
[...] very first result was this: http://cowburn.info/2008/01/13/get-file-extension-comparison/ article by somebody called [...]
Congratulations on the first google result for search “php get file extension”. I love this simple snippet of code and wouldn’t have found it by just browsing through php-manual on my own.
Nice blog post. Just what I was looking for.
Thanks, for the simple, straightforward post! It was helpful!
I am looking for these comparison for a while. Many thanks for suggestion the best way to get file extension, This is so easy to use and no complicate. Next time I write code, I will use PATHINFO_EXTENSION ^^
Very good article. I think the right way to go is pathinfo way. Others are just workaround.
Great write up/discussion.
Many times, I want to parse the extension and get the file name (sans the extension) as well. I typically use:
$ext = substr(strrchr($filename, '.'), 1);$file = rtrim($filename, '.'.$ext);
This method also allows you to define the separator (‘.’ or ‘|’ or ‘str’, etc.) for other types of applications where you are looking to split a string into two parts based on the last defined character (or string/pattern).
Eric, you could also just use
pathinfo()as outlined above andbasename()functions, to get the extension and file name respectively. Being allowed to use alternative separators makes little sense for file names/extensions, and if you’re working with strings that are not file names then it doesn’t make sense to use file functions.Peter,
Okay, I concede, in that this is a “file” and “extension” discussion.
But… it’s semantics! The so called “file” functions have less to do with files, and more to do with string parsing, no?
They are intended for files, if they’re used any other way then that is entirely the developer’s choice.
[...] recently need to get the file extension from a string. After a quick Google search I found this page which mentions 5 different methods for getting a file extension. While the author does make it [...]
Thanks for the post. I am glad I found your article because I want the fastest script tempered with readability.
I liked your article!
But I have one comment on the double extensions (like image.php.gif):
.gif will be returned by both of the following lines of code:
$ext = substr($filename, strrpos($filename, ‘.’) + 1);
$ext = strrchr($filename, ‘.’);
I’m not trying to debate which method is best, but I wanted to point out that there are other ways to figure out the last extentension with multiple dots in a filename.
This is why it’s so wonderful that nothing ever goes away on the web. This article was written in 2008, and here we are in the waning days of 2011, and BOOM!
It helped me.
I found that the new php was giving me fits about my venerable
end(explode(‘.’, $filename) method.:
( ! ) Strict standards: Only variables should be passed by reference in /Users/xxx.php on line 689
This was much easier than wrapping my head around the use of & and passing things by reference…
Be careful when using pathinfo to get the extension: it returns the case-sensitive extension.
So a check for
$file['extension'] == 'jpg'will returnfalse
when the file is named
‘pic.JPG’
Just use
mb_strtolower()on$file['extension']as a workaround.Thanks for the comment, Martin. I’d just like to note that
pathinfo()doesn’t return “the case-sensitive extension”, it just returns the extension.Of course, the file extension may be upper, lower or mixed case but how you deal with that, if at all, is application-specific and not something that
pathinfo()should care about. There are several built-in string functions for comparing strings case-insensitively.Thanks, it helped me a lot.
Thanks! My current project will like this
Handy tip, thanks!
Very good concept. Thanks a lot. explode() worked out fine.
Big thanks! Nice write up too.
Thanks so much for your research. I was able to utilize your findings on a project I’m working on currently.
Exactly what I needed. Thank you!
Beautifully explained. Thanks!
The only thing that fails is if the path has a query line attached. Like
- it will output ‘txt’
Just a note. easy to fix offcourse:
if( strpos($p,"?") != '' ) $p = substr($p, 0, strpos($p,"?") );
return pathinfo($p, PATHINFO_EXTENSION);
}
echo getFileExtension("http://mysite.com/page.php?file=msg.txt")
- will output ‘php’
Thanks for the heads up on PATHINFO_EXTENSION!
Jacob, this is because
pathinfo()works on filesystem paths not URLs. For your example with a URL, you could get the path by usingparse_url().$ext = pathinfo($path, PATHINFO_EXTENSION);
Hi,
does the pathinfo() method work with files in the $_FILES array in http post/get?
being unsure, i’m using the explode way for now.
thanks for this post, it’s cool.
Dan, yes
pathinfo()will work with paths in$_FILES. It just takes a string containing a file path and doesn’t care a jot where it came from.Hey, just here to drop a “Thank You!” for showing us this snippet of code. Very simple, but beats the way I was doing it by a mile (r by milliseconds, which is, a lot in terms of a script). Thank you!
yo Peter
pathinfo() is not secure
http://www.madirish.net/?article=232
publo,
pathinfo()is “secure” in the sense that it does exactly, and only, the job requested of it as documented. If you try to usepathinfo()in a manner other than it is supposed to be used, then it is the developer’s failing. With regards to that article, the developer is simply demonstrating a completely incorrect method for validating the input:pathinfo()is still doing its job correctly. The function is not insecure, the developer trying to use it where it is not appropriate, is.Wow a high level programming discussion, i came…
Mr Doe, happy to be of service. Don’t forget to clean up.
THANKS!
My site uploads pictures. Some are .jpeg.
The programmer went through multi line code to extract .ext and eventually used code that grabbed the last 3 characters; thereby messing up .jpeg files.
I deleted 4 lines, used pathinfo() and works perfectly.
Programmer wanted to know where I learned the great code!
Thank you Peter.
ps had looked at over 40 articles for extracting .ext.
[...] http://cowburn.info/2008/01/13/get-file-extension-comparison/ [...]