17th DEGREE

I just came across a really odd error while matching for some specific characters in PHP. I found the error while using both preg_match() and ereg().

With preg, the error was this:
Warning: preg_match() [function.preg-match]: Compilation failed: range out of order in character class at offset 11 in /temp.php on line 5

With ereg, the error was this:
Warning: ereg() [function.ereg]: REG_ERANGE in temp.php on line 13

Both were caused by the same error or bug. I’m not sure which.

Here is the bad code:
$userid = 'abcDEF_-.';
if(preg_match('/[^a-zA-Z0-9_-\.]/', $userid)) {
echo 'bad';
} else {
echo 'good';
}
 
if (ereg("[^a-zA-Z0-9_-.]", $userid)) {
echo 'bad';
} else {
echo 'good';
}


That all seems correct, doesn’t it? It is checking to see if the userid has something other than those characters.

The problem? The dash, or hyphen, being before the period. It thinks it’s a range, like you see in a-z. This may not be a bug, per se, but it’s certainly not smart enough for me.

The solution? Simply put the dash at the end of the regex.

$userid = 'abcDEF_-.';
if(preg_match('/[^a-zA-Z0-9_\.-]/', $userid)) {
echo 'bad';
} else {
echo 'good';
}
 
if (ereg("[^a-zA-Z0-9_.-]", $userid)) {
echo 'bad';
} else {
echo 'good';
}


Hope this helps out someone else in the future.

This entry was posted on Thursday, June 29th, 2006 at 10:58 am and is filed under Programming. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.