preg_match with brackets in expression

[Untam3d]

Ok, I am using this code to check the form for invalid characters:

if(preg_match('/^[a-zA-Z0-9]$/', $char)){
REST OF MY CODE HERE

This is what $char is:

$char = $_POST['charname'];

And $char connects to a form. My problem is that, I only want a-z, A-Z, 0-9, and [ and ] (aka brackets) allowed.

So far only a-z, A-Z, and 0-9 are allowed... I am not sure how to add brackets to that. Help please? Thanks!

[Dormilich]

escape the brackets with a backslash.

[Untam3d]

I don't want to "escape" the brackets, I want to add brackets to the exception. Currently the exception is all lowercase or capital alphabetical letters, and all 10 numbers. I want to also add ] [ to the exception [the two brackets]. How do I do this? Thanks, and I appreciate the response.

[Dormilich]

@Untam3d
guess how you do that.....

preg_match('§^[a-z0-9\[\]]$§i', $char)

... by escaping

[Untam3d]

@Dormilich
Got it! Thanks a whole lot Dormilich.