What is the fastest way to find the occurrence of a string in another string? [duplicate]

Answer 1

The faster way is:

if (strpos($haystack, $needle) !== false)

The case insensitive versions should obviouslly be slower (at least 2x slower, I expect).

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strncmp() / substr() can possibly perform better iff you're checking if $haystack starts with $needle and if $haystack is considerably long (> hundreds chars or so).

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Benchmark:

• strpos() vs. strncmp() = short | long

See other benchmarks @ http://net-beta.net/ubench/ (search for strpos).

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A pratical example where this kind of optimizations (kind of) do matter - calculating hashcashes:

$count = 0;
$hashcash = sprintf('1:20:%u:%s::%u:', date('ymd'), $to, mt_rand());

while (strncmp('00000', sha1($hashcash . $count), 5) !== 0)
{
    ++$count;
}

$header['X-Hashcash'] = $hashcash . $count;

Answer 2

strpos seems to be in the lead, I've tested it with finding some strings in 'The quick brown fox jumps over the lazy dog':

• strstr used 0.48487210273743 seconds for 1000000 iterations finding 'quick'
• strpos used 0.40836095809937 seconds for 1000000 iterations finding 'quick'
• strstr used 0.45261287689209 seconds for 1000000 iterations finding 'dog'
• strpos used 0.39890813827515 seconds for 1000000 iterations finding 'dog'

<?php

    $haystack = 'The quick brown fox jumps over the lazy dog';

    $needle = 'quick';

    $iter = 1000000;

    $start = microtime(true);
    for ($i = 0; $i < $iter; $i++) {
        strstr($haystack, $needle);
    }
    $duration = microtime(true) - $start;
    echo "<br/>strstr used $duration microseconds for $iter iterations finding 'quick' in 'The quick brown fox jumps over the lazy dog'";

    $start = microtime(true);
    for ($i = 0; $i < $iter; $i++) {
        strpos($haystack, $needle);
    }
    $duration = microtime(true) - $start;
    echo "<br/>strpos used $duration microseconds for $iter iterations finding 'quick' in 'The quick brown fox jumps over the lazy dog'";

    $needle = 'dog';

    $start = microtime(true);
    for ($i = 0; $i < $iter; $i++) {
        strstr($haystack, $needle);
    }
    $duration = microtime(true) - $start;
    echo "<br/>strstr used $duration microseconds for $iter iterations finding 'dog' in 'The quick brown fox jumps over the lazy dog'";

    $start = microtime(true);
    for ($i = 0; $i < $iter; $i++) {
        strpos($haystack, $needle);
    }
    $duration = microtime(true) - $start;
    echo "<br/>strpos used $duration microseconds for $iter iterations finding 'dog' in 'The quick brown fox jumps over the lazy dog'";

?>

Answer 3

From the PHP Docs:

Note:

If you only want to determine if a particular needle occurs within haystack, use the faster and less memory intensive function strpos() instead.

I'm willing to take their word for it :)

Answer 4

According to the php manpages, strpos is faster and less memory intensive than strstr.

Answer 5

Trick question. They do two different things. One returns the substring, the other returns the starting position of the substring withing the string. The real answer is you are comparing apples to oranges, use which one you need.

Answer 6

If the string A against which you want to find an occurrence of a pattern B, then the fastest way is to build a Suffix Tree of A and perform against it searches for B.