Question

As in HTML 4 specification noted that :

ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens (“-“), underscores (“_”), colons (“:”), and periods (“.”).

How can I validate an ID/NAME token is valid by using PHP?

Answer 1

I suppose a regular expression such as this one could do the trick :

^[A-Za-z][A-Za-z0-9_:\.-]*

For more informations, see the following section of the manual : Regular Expressions (Perl-Compatible)

And to use that, in PHP, you’d have to use the preg_match() function :

if (preg_match('/^[A-Za-z][A-Za-z0-9_:\.-]*/', $id)) {
    // valid
}