preg_match breaks with more then 5100 characters

Question

I'm trying to match for plain text here is the regex

   $variable = "newteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewteststorynewtest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   $result = preg_match('/^([a-zA-Z0-9 \n\r,!@#\$\.\+\-%\^&\(\)~`\'":;_=\?\\/\|\<\>\*\{\}])+$/',$variable);

and it fails and I can't figure out why

I'd break too if I had to deal with a string that long... – Ignacio Vazquez-Abrams Mar 10 '11 at 17:43 — Ignacio Vazquez-Abrams, Mar 10 '11 at 17:43
You forgot a semicolon at the end of your first line. – Thai Mar 10 '11 at 17:43 — Thai, Mar 10 '11 at 17:43
That's why it's not an answer. – Ignacio Vazquez-Abrams Mar 10 '11 at 17:45 — Ignacio Vazquez-Abrams, Mar 10 '11 at 17:45
I missed the semicolon when I was copying – mcgrailm Mar 10 '11 at 17:45 — mcgrailm, Mar 10 '11 at 17:45
@ Ignacio Vazquez-Abrams good poing 8 ^ ) – mcgrailm Mar 10 '11 at 17:45 — mcgrailm, Mar 10 '11 at 17:45

score 4 · Accepted Answer · answered Mar 10 '11 at 17:47

A few suggestions to try:

Move the + inside of the capture group so it needs to do less internal shifting.

$result = preg_match('/^([a-zA-Z0-9 \n\r,!@#\$\.\+\-%\^&\(\)~`\'":;_=\?\\/\|\<\>\*\{\}]+)$/',$variable);

Why capture at all?

$result = preg_match('/^[a-zA-Z0-9 \n\r,!@#\$\.\+\-%\^&\(\)~`\'":;_=\?\\/\|\<\>\*\{\}]+$/',$variable);

Why not just negate so it doesn't need to build up the internal state:

$result = !preg_match('/[^a-zA-Z0-9 \n\r,!@#\$\.\+\-%\^&\(\)~`\'":;_=\?\\/\|\<\>\*\{\}]/',$variable);

What I think's happening is that you're over-running the internal buffer that pcre is using to keep track of the state. Give a try using a negated preg match (since you're not using the captured group anyway, all you care is if it has an invalid character)...

And a nitpick: $.+^()?<>*{} don't need escaping at all inside of a character block. The only ones that do are your delimiter (/), - and a leading ^ character (which doesn't apply to you.

thanks for making my headache go away it looks much better now $result = !preg_match('/[^a-zA-Z0-9 \n\r,!@#$.+\-%^&()~`\'":;_=?\/|<>*{}]/',$variable); — mcgrailm, Mar 10 '11 at 18:14

score 0 · Answer 2 · answered Mar 10 '11 at 17:47

You are matching too long text. It usually happen to me too when parsing very long subpatterns. Here are some things that you can try:

Remove the capturing parentheses:

$result = preg_match('/^[a-zA-Z0-9 \n\r,!@#\$\.\+\-%\^&\(\)~`\'":;_=\?\\/\|\<\>\*\{\}]+$/',$variable);

It might not work, as it still has to match very long text. Another way to do this is:

Do a negative match that matches only one character not in your set, and make sure that it does not match.

$result = preg_match('/[^a-zA-Z0-9 \n\r,!@#\$\.\+\-%\^&\(\)~`\'":;_=\?\\/\|\<\>\*\{\}]/',$variable);

$valid = !$result && strlen($variable) > 0;

P.S. Your code runs fine in my computer.

preg_match breaks with more then 5100 characters

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