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Doc Bug #29039 ereg {0,255} limited to 255 ... and not documented
Submitted: 2004-07-06 23:41 UTC Modified: 2004-07-12 10:09 UTC
Avg. Score:3.8 ± 1.5
Reproduced:3 of 4 (75.0%)
Same Version:3 (100.0%)
Same OS:1 (33.3%)
From: info at smithfieldentertainment dot com Assigned:
Status: Wont fix Package: Documentation problem
PHP Version: Irrelevant OS: UNIX
Private report: No CVE-ID: None
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 [2004-07-06 23:41 UTC] info at smithfieldentertainment dot com
I sent the following email to Mehdi Achour <>



I discovered (the hard way after hours of code troubleshooting) that ereg/eregi/etc. functions have a very useful but LIMITED length function.

It seems that while the ereg functions will search for matches in (any?) length code, the length limiter {0, 255} is limited to 255.


I was trying to match lengths of 350 and 800? but couldn?t figure out why I was getting an error.  There?s no documentation on this anywhere that I could find.


Please add it to all applicable regular expression match items that it applies to.



-- CJ Greiner




Reproduce code:
if (eregi("^([a-z0-9 $&*?\'.-]{100,300})$", $register_data[register_summary], $ereg_results) == FALSE) {
  $error_message .= '<br>Subject Summary:  Please use only letters, numbers, and punctuation: \'-$&amp;*?<br>';

Expected result:
if the user input $register_data[register_summary] does not match the regular expression OR is ouside the acceptable length range of 100-300 letters, then the expression should return FALSE and assign an $error_message.

Actual result:
Even when the user input for $register_data[register_summary] had acceptable characters AND had acceptable lengths...

The code failed because the max length of 300 {100, 300} was causing a FALSE or FAIL.

I experimented with the length until I brought it down to 255... then it worked.

This limit is not documented anywhere.
There should be no limit... or at least a much higher limit, since the matching expression will work on a much longer string if no length limit is placed in it.



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 [2004-07-08 13:19 UTC]
We have discussed this and we decided not to document this behaviour, has this is cleary explained in the man page.
 [2004-07-11 08:32 UTC] info at smithfieldentertainment dot com
It seems the only useful information about regular expressions in PHP can be found at:
PCRE Pattern Syntax.

It DOES discuss the 
{ - start min/max quantifier, and the
} - end min/max quantifier

... but does not mention any limits on PHP's ability to process strings greater than 255 in length.

The PHP manual could use additional helpful info on regular expressions.  It would also be helpful if the information you've already included was more complete.
Limits like {0, 255} ARE important to programmers.
I was able to work around it... but it took a few hours to find the limitation in the first place, and several lines of code to work around it once I knew what the problem was. 

Please either fix PHP, or fix its documentation.

Thank you.
 [2004-07-12 10:09 UTC]
PCRE Pattern Syntax is documentation to Perl Compatible Regular Expressions, not to POSIX Regular Expressions. There's no such limitation in PCRE.

In Introduction part of is link to regular expression documentation - man page regex.7 where is written: "A bound is `{' followed by an unsigned decimal integer, possibly followed by `,' possibly followed by another unsigned decimal integer, always followed by `}'. The integers must lie between 0 and RE_DUP_MAX (255(!)) inclusive".
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