[RESOLVED] regular expression isn't quite working right

dbomb101

I recently used regular expression to do some validation for the registration form for my site

if (!preg_match("/^[a-zA-Z]/", $_POST['forename'])) 
{	
$errormsg.="You need to enter a forename<br/>"; 
}

I use code above to check to make sure that there are no numbers are allowed to be entered but it doesn't work

any help would be much appreciated
🙂

laserlight

Instead of stating what you do not want to allow, state what you want to allow, and nothing else. Then check that the entire input consists of what you want to allow.

dbomb101

sorry didn't explain properly, I wrote the code so that it only allows letters but when i test it with numbers it still says it is valid

dbomb101

I mean to sat that when i test it with a combination of numbers and letters it allows it.

laserlight

dbomb101 wrote:
I wrote the code so that it only allows letters but when i test it with numbers it still says it is valid

If you only want to allow letters, use [man]ctype_alpha/man. That said, the problem with your regex pattern is that it asserts the start of the input. If you change it to /[^a-zA-Z]/ then it will work.

By the way, use single quotes for regex patterns.

dbomb101

Thanks for the function, much easier to deal with than regular expression much apprceiated 🙂

nrg_alpha

laserlight;10925108 wrote:
If you only want to allow letters, use [man]ctype_alpha/man. That said, the problem with your regex pattern is that it asserts the start of the input. If you change it to /[^a-zA-Z]/ then it will work.

By the way, use single quotes for regex patterns.

Granted, depending on the locale, ctype_alpha might not be sufficient 'as is'. If the goal is to in fact only allow a-zA-Z, it might be necessary to either:

a) explicitly state the letter range (as you have shown with your pattern),

b) declare setlocale(LC_CTYPE, 'C'); prior to using ctype_alpha (or any other ctype functions / regex patterns with character classes like \d, \w, etc) to ensure the locale in question doesn't botch things up with unexpected results (in this case, think along the lines of accented characters).

<--- hates locale issues :mad: