By Harry Fuecks

Validation with CType

By Harry Fuecks

What happens when you take you eye off the ball? The CType extension becomes a default part of PHP!

Have to confess I’ve never touched them until recently and was stuck in a “validation = regular expressions” mindset. What puzzles me is I haven’t seen anyone else using them either – most libraries doing some validation, including QuickForm and Validate all use regular expressions. Anyone know why? It’s not hard to use them but fall back to regular expressions for older PHP versions.

The CType functions are wrappers for ctype.h, a standard part of C, so are, effectively, very well tested.

The point is, for validating certain basic types of data, they do a better job than regular expressions, being both faster and supporting international character sets. The also make your code more “declarative” in nature – it’s pretty clear what ctype_digit() does while ‘/(^-?dd*.d*$)|(^-?dd*$)|(^-?.dd*$)/’ is less obvious.

For example say you have a field in your form for “First Name”. Using regular expressions, you’d probably validate it something like;

if ( !preg_match('/^[a-zA-Z]*$/', $first_name) ) {
die ('Alpha characters only please!');

Now that’s fine if your name is Joe but what if your name is H

  • Wow thats a good tip! Thanks!

  • I have never heard of these functions. Nice find!

  • Hmmm – perhaps part of the reason no ones using these is because they don’t exist, according to the contents page of the manual: . The do turn up in the function index though:

  • nucleuz

    A very good thing to have indeed when doing a multi-language application :) Been around for a while though ( a 4.3.2 version has it by default here ) so it’s a bit weird to see that it isn’t in the main docs.

  • Dangermouse

    Wow, i never knew about ctype, thanks!

  • khlo

    Good find, seems to be on the PHP index at now “XV. Character Type Functions”. Will be trying later, never been fan of regexp

  • Nola

    I used this:

    $first_name = "H

  • I get “Alpha characters only please!”

    I guess that’s the locale settings your OS is running. You probably want to explore setlocale() to set the country to somewhere like Norway. I need to do some more research on setlocale and all the ins and outs on Linux vs Windows. Will blog it some time.

  • Tim Strehle

    “supporting international character sets” – well, yes, but I’ve done some investigation and it seems to me that ctype does not support multibyte character encodings.

    So for UTF-8 applications, you cannot use ctype_alpha() and the like…

  • nucleuz

    Tested this out on OSX 10.3.2 ( Norwegian edition ) and as the previous comment says: this doesn’t work with H

  • NativeMind

    no multibyte applications? man, that’s rough — come on folks, multibyte is essential to a successful API

  • Knew of it but didn’t know what it did ;)

    But I’d still proberly use Reg Exp anyways, just out of habit if nothing more :lol:

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