Edit report at http://bugs.php.net/bug.php?id=52788&edit=1
ID: 52788
User updated by: reevsey at gmail dot com
Reported by: reevsey at gmail dot com
Summary: preg_match not matching last backslash '\'
Status: Bogus
Type: Bug
Package: *Regular Expressions
Operating System: ALL
PHP Version: 5.3.3
Block user comment: N
New Comment:
Thanks for your speedy reply. Yes your absolutely right and sorry for my
mistake.
The code fragment I posted is from a larger code base and for whatever
reason backslash was the only character that was not being matched.
Other invalid characters '#$%^&' etc. even with valid chars beforehand
were being matched, which made it seem like a bug.
Anyway replacing the expression makes it work.
Once again thanks for your time and the suggested use of the other
functions, the expression posted will form a larger expression evently
and indeed will need the anchoring back; my mistake.
Previous Comments:
------------------------------------------------------------------------
[2010-09-07 08:03:00] ras...@php.net
And if you replace that backslash with any other character that is not
in your
range, you will see the same thing. It has nothing to do with the
backslash.
Your regex is simply completely wrong.
Your regex says:
>From the start of the string ^
Find me 0 or more characters that are not [^0-9a-zA-Z]*
Until the end of the string $
Your problem is that you have anchored it to the start of the string.
In each
of your "not matched" cases, you have a valid char as the first char.
What you probably meant to write was:
'#[^0-9a-zA-Z]+#'
By not anchoring your regex to the start or end of the string, you are
telling
it to look for invalid characters anywhere in the string. And you want
+
instead of * because you want to match at least 1 invalid char, not 0.
By the way, there are much quicker ways of doing this if your list of
valid or
invalid chars is finite. See strpbrk and strcspn.
------------------------------------------------------------------------
[2010-09-07 07:37:44] reevsey at gmail dot com
Description:
------------
preg_match() does not match the last backslash at the end of a subject
string.
I'm using the pattern "#^[^0-9a-zA-Z]*$#" to filter out any characters
from user input other than alphanumerics.
The Problem I'm seeing is if there is a backslash \ as the last
character with valid characters before it, then preg_match() does not
match it.
Example input:
\ = matched.
\\ = matched.
a\a = matched.
&@$ = matched.
a\ = not matched.
0\ = not matched.
A\ = not matched.
abc\ = not matched.
etc...
Test script:
---------------
// Obviously taking into account here that backslash \ is an escape
char.
// SO double the backslash.
$userInput = "a\\";
if (preg_match("#^[^0-9a-zA-Z]*$#", $userInput))
{
echo "Invalid input";
}
else
{
echo "Good to go!";
}
// If you negate the regular expression to "#^[0-9a-zA-Z]*$#" and change
the
// test statement to be:
// if (!preg_match("#^[0-9a-zA-Z]*$#", $userInput)) {}
// it works as expected.
Expected result:
----------------
Expected result: Invalid input
Actual result:
--------------
Actual result: Good to go!
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/bug.php?id=52788&edit=1
