Sometimes it seems like everyone has a different opinion on something, and the best function for comparing simple strings in PHP is one of those things. The four primary ways are ereg(), preg_match(), strstr(), and strpos(). For a simple comparison, any of these will work, but, once you start doing a great deal of string comparison, the speed of these functions comes into play. Even the PHP site suggests preg_match() on the ereg() page:
Note: preg_match(), which uses a Perl-compatible regular expression syntax, is often a faster alternative to ereg().
Then, if you check the preg_match() page, it says:
Tip: Do not use preg_match() if you only want to check if one string is contained in another string. Use strpos() or strstr() instead as they will be faster.
I decided the best answer was to test each one and see what I came up with.
My test was to search for a five character string within a string of approximately 60,000 characters. The test was originally going to run 10,000 times, but I ended up doing that 25 times for each function, taking the average in order to try to limit variation.
| Results | |
| ereg | .956 |
| preg_match | .050 |
| strstr | .222 |
| strpos | .033 |
Occasionally, preg_match() would come very close to beating strpos(), but overall the results showed strpos() to be the fastest, followed closely by preg_match(), then strstr(), and pulling up the rear was ereg(). It looks like strpos() is definitely the best function for a quick check, and preg_match() is the answer for any searches that require a little more sophistication, but the differences were minimal. Keep in mind, these results represent 10,000 searches of a nearly 60,000 character string. Most applications/scripts would never come close to that, so the function choice isn’t a major concern.
7 Responses to “The Speed Of String Comparison Functions In PHP”
- 1 Pingback on Nov 28th, 2007 at 5:09 pm
This is the great article very useful for writing optimized code.
Thanks for the results.
Which PHP version was used for this test?
I can’t say for absolutely sure since I didn’t make note of it at the time (but I definitely should have!), but I believe it was 5.2.0, since that was the most current version at the time.
You may see differente results for many small searches, since the time it takes to run each function probably is time = setup constant + search time.
It would be interesting to see the results summarized for various search lengths, particularly searching short strings.
Thanks for running the test and posting it !
Do you know whats the average speed of preg_replace?
Is it right up there with preg_match? preg functions might be slow because the it scans the string several times depending on how many () you have in the regex.
Hi Dudewtf, I haven’t specifically tested preg_replace in a controlled environment, but I’d suspect it is only slightly slower than preg_match. Finding matches is the hard part; after that, it’s just string replacement. Assuming your string isn’t excessively long, the operation is fairly trivial.