QUOTE
(?:this|that)
What's the ?: there for? I don't see any difference when validating various dummy strings against it.
Full Version: A regex question that's been baffling me.
I've seen this in many applications that use regex, but I can't seem to figure out what it is.
What's the ?: there for? I don't see any difference when validating various dummy strings against it.
What's the ?: there for? I don't see any difference when validating various dummy strings against it.
Usually when you create a group, a backreference is also created. For example, if you had the regex (this|that), and it matched, then the backreference would contain "this" or "that", whichever.
The ?: makes the grouping work the same, but tells the regex engine not to create a backreference. See here for more info.
So if you had (this|that)_([0-9]+), the first backreference would contain either "this" or "that", the second would be a number. The expression (?:this|that)_([0-9]+) would only contain one backreference, and that would be the number.
The ?: makes the grouping work the same, but tells the regex engine not to create a backreference. See here for more info.
So if you had (this|that)_([0-9]+), the first backreference would contain either "this" or "that", the second would be a number. The expression (?:this|that)_([0-9]+) would only contain one backreference, and that would be the number.
Ah, I see now!
Returns '3'.
Thanks!
CODE
<?php
echo preg_replace("<(?:this|that)_([0-9]+)>is", "$1", "this_3");
?>
echo preg_replace("<(?:this|that)_([0-9]+)>is", "$1", "this_3");
?>
Returns '3'.
Thanks!
QUOTE(Veracon @ May 8 2005, 11:09 AM) 
Ah, I see now!
Returns '3'.
Thanks!
CODE
<?php
echo preg_replace("<(?:this|that)_([0-9]+)>is", "$1", "this_3");
?>
echo preg_replace("<(?:this|that)_([0-9]+)>is", "$1", "this_3");
?>
Returns '3'.
Thanks!
Are you sure < and > are good brackets? I would suggest matching characters, such as #.
CODE
<?php
echo preg_replace("#(?:this|that)_([0-9]+)#is", "$1", "this_3");
?>
echo preg_replace("#(?:this|that)_([0-9]+)#is", "$1", "this_3");
?>
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