Regular expression for allowed characters

Question

i need to check, if the string in my PHP code contains only a specified list of characters. But as some of them might need scape, i just can't get it to work. I have tried everything, but it just doesen't work...

The required validation is:

0-9
A-Z
a-z
chars: .%^&()$#@!/-+/

Basicaly, i want to check if there is an unknown ascii character (i don't know if there is a function to do that already).

My code is like this now:

if(preg_match("/[A-Za-z0-9\.\#\-\+\*\\\/\=\_\%\$\(\)]/", $cmd) === false)

So, all of the chars are special?

score 2 · Answer 1 · answered Aug 04 '12 at 19:16

2

No, all of those characters are not special. If you're unsure, you can let PHP do the escaping for you with preg_quote():

$regex = '/[A-Za-z0-9' . preg_quote( '.%^&()$#@!/-+/', '/') . ']+/';
if( !preg_match( $regex, $cmd))

Also, preg_match() returns an int, and you're doing === on a boolean, which will never hold true, since they will never be of the same type. You can simply check for if( !preg_match()).

answered Aug 04 '12 at 19:16

nickb

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Nice! I didn't know that PHP has a function that scaped things! Thanks! Worked perfecly... – Ivan Seidel Aug 04 '12 at 19:22

score 1 · Accepted Answer · edited May 23 '17 at 10:34

1

You might be missing a * at the end of the regexp. Also you could instead have the set expressed like [\x00-\x7F] (taken from here).

This should work:

[\x00-\x7F]*

edited May 23 '17 at 10:34

Community

1
1

answered Aug 04 '12 at 19:16

juan.facorro

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chars 0 to 7F are 'human readable'? is that why? @juan.facorro – Ivan Seidel Aug 04 '12 at 19:23
No, they're not all human readable. Character 0 is the NULL character, and the rest are on an ASCII table. – nickb Aug 04 '12 at 19:25
nice... i will test this way also! Thanks – Ivan Seidel Aug 04 '12 at 19:26
@Ivan And it will match **many, many more** characters than in your question. – nickb Aug 04 '12 at 19:37

score 0 · Answer 3 · answered Aug 04 '12 at 19:14

0

if(preg_match("/[.%^&()$#@!/+-a-zA-Z\d\s]+/", $cmd) === false) and if you need anchors if(preg_match("/^[.%^&()$#@!/+-a-zA-Z\d\s]+$/", $cmd) === false)

answered Aug 04 '12 at 19:14

burning_LEGION

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Regular expression for allowed characters

3 Answers3

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