Bug in preg_match() ? View as Markdown

Hi,

This script:

<?
$line = "Use operator m// for matching strings";
$pattern = "m//";

    if(preg_match("/$pattern/", $line, $match)) {
            print $match[0]."\n";
    }

?>

There is no bug here!

The final pattern is "/m///". When using // as delimeters, you must escape
them, so you would need to set
$pattern="m//"

or
using other delimeter such as '~':
preg_match("~$pattern~",...)

Nuno

• Thus wrote Michael Spector:

Hi,

This script:

<?
$line = "Use operator m// for matching strings";
$pattern = "m//";

    if(preg_match("/$pattern/", $line, $match)) {
            print $match[0]."\n";
    }

?>

outputs the following error:

<br /> <b>Warning</b>: Unknown modifier '/' in <b>/home/michael/bug.php</b> on line <b>5</b><br />

I thought it should find the match "m//" ...

Can you say, why search of the ending delimiter in a pattern cannot
be performed in a simple way, as you can see in the attached patch ?

Because of side effects like this:

$pattern = "Foo//i";
if(preg_match("/$pattern", $line, $match)) {

With your patch the preg_match has silently turned into a
caseINsensitve search.

Just use preg_quote($pattern, '/');

Curt

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