preg_match vs. ereg

Stinger51

ereg() is exhibiting some strange behavior on my system (to just downright not working in some cases). So I'm learning how to use preg_match instead. Unfortunately, the documentation is pretty scant on preg_match.

I've set up a simple ISO 9000 date (yyyy-mm-dd) checking function (borrowing some syntax from the way ereg does it) as :

if (preg_match('/^{([0-9]{4})-([0-9]{2})-([0-9]{2})$/',} $date))
// good date
else
// bad date

It seems to be working just fine during testing for ISO dates. But I want to be sure there aren't some hidden "gotcha's" with the syntax here before I get to carried away. Can I safely assume that regular expressions work pretty much the same way for preg_match as they do for ereg?

Thanks in advance

swr

You might find better docs on PCRE's on perl-related sites.

Your expression looks like it should work fine.

You can use \d instead of [0-9]. Also, you can drop the regular brackets unless you actually want to extract the year month and day (which would require a third argument to preg_match).

I can't really speak to differences, as I always use PCREs (I learned Perl long before I learned PHP).

if (preg_match('/^\\d{4}-\\d{2}-\\d{2}$/', $date)) {
    // good date
}
else {
    // bad date 
}

or...

if (preg_match('/^(\\d{4})-(\\d{2})-(\\d{2})$/', $date, $matches)) {
    $year = $matches[1];
    $month = $matches[2];
    $day = $matches[3];
}
else {
    // bad date
}

Stinger51

I guess you are saying that preg_match pretty much follows the PERL syntax then?

Also, I'm trying to develop a function to check U.S. zip codes, both the 12345 and the 12345-6789 type. So I'm thinking something like this will work :

if (preg_match ( '/^{([0-9]{5})$/'} | '/^{([0-9]{5})/([0-9]{4})$/',} $zipcode) )

should work?

Thanks in advance.

swr

Yes, it follows the Perl syntax. The "p" in "preg" stands for Perl. The [man]PCRE[/man] manual page has info (PCRE = Perl Compatible Regular Expressions).

The vertical bar means bitwise OR in PHP, so that definitely won't work. It needs to be part of the regular expression.

Something like this:

preg_match( '/^{(\d{5}|\d{5}-\d{4})$/',} $zipcode)

Or this:

preg_match( '/^{\d{5}(|-\d{4})$/',} $zipcode)

The brackets are for specifying a group, the vertical bar seperates the allowed forms. In the second example, the first part of the group allows a blank string, the second part allows the "-1234".