In PHP I'd like to be able to limit the number of characters around a word I'm trying to match. Let's say:

• $content contains the full text
• $look_for contains the string I want to search for in that full text

I want this to be language agnostic, including languages like chinese that don't have space separators. The full text will be utf8. The following code is what I tried:

preg_match("/(.*){0,10}$look_for(.*){0,10}/i", $content, $matches);

With this the $matches is empty. Isn't the {0,10} supposed to be limiting the characters around the intended word?

CodePudding user response：

(.*){0,10} is what is known as "catastrophic backtracking", use (.{10}) instead.

<?php

$content = 'aaaaaaaabbbbbbbbcccccccc the quick brown fox jumps over the lazy dog xxxxxxxxyyyyyyyyzzzzzzzz';

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

$regex = '/(.{10})' . $look_for . '(.{10})/i';

$matches = [];

preg_match($regex, $content, $matches);

var_dump($matches);

Results in:

array(3) {
    [0]=>
    string(63) "bcccccccc the quick brown fox jumps over the lazy dog xxxxxxxxy"
    [1]=>
    string(10) "bcccccccc "
    [2]=>
    string(10) " xxxxxxxxy"
}