Regular expression greedy max string?

PHP
1

Hi~ All this is my Tesing code

<?php
$html1 = '<table>';
$html2 = '01234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234';
$html3 = '</table>';

for ($i = 40; $i <= 50; $i++) {
    $html = $html1;
    for ($j = 0; $j <= $i; $j++) {
        $html.= $html2;
    }
    $html.= $html3;
    if (preg_match('/<table.+?<\\/table>/is', $html)) {
        echo strlen($html) . "=>success<br>";
    } else {
        echo strlen($html) . "=>fail<br>";
    }
}

Result:
85090=>success
87165=>success
89240=>success
91315=>success
93390=>success
95465=>success
97540=>success
99615=>success
101690=>fail
103765=>fail
105840=>fail

Is the max string is 100012?

2

It looks to me like you’re hitting the backtrack limit (defaults to 100,000). Check for yourself by seeing if the error code returned from [url=http://php.net/preg_last_error]preg_last_error() is PREG_BACKTRACK_LIMIT_ERROR.

How to alleviate the problem is up to you, raise the limit or change the way that the code works so that it does not backtrack beyond the limit.

3

Thank you!:slight_smile:

find php.ini pcre.backtrack_limit=1000000