How to change PHP's eregi to preg_match

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How can I convert ereg expressions to preg in PHP?

I need help, below is a small VERY basic regex to somewhat validate an email, I do realize it does not work the greatest but for my needs it is ok for now.

It currently uses PHP's eregi function which php.net says is now a depreciated function and I should use preg_match instead, simply replacing erei with preg_match does not work, can someone show me how to make it work?

function validate_email($email) {
    if (!eregi("^[[:alnum:]][a-z0-9_.-]*@[a-z0-9.-]+\.[a-z]{2,4}$", $email)) {
        echo 'bad email';
    } else {
        echo 'good email';
    }
}
function validate_email($email) {
    if (!preg_match("^[[:alnum:]][a-z0-9_.-]*@[a-z0-9.-]+\.[a-z]{2,4}$", $email)) {
        echo 'bad email';
    } else {
        echo 'good email';
    }
}

Note that you should not use this regex to validate e-mail; it is severely outdated. — Piskvor left the building, Oct 22 '14 at 15:33
@Piskvor I agree, this question is nearly 5 years old too =) you should post an updated answer if you like and I can always change the "selected" answer to the best approach — JasonDavis, Oct 22 '14 at 16:02
It's IMHO outside of the scope of the ereg/preg issue; commenting seems sufficient to me. — Piskvor left the building, Oct 22 '14 at 16:40

score 32 · Accepted Answer · edited Apr 28 '11 at 22:12

32

Perl-style regex patterns always need to be delimited. The very first character in the string is considered the delimiter, so something like this:

function validate_email($email) {
    if (!preg_match("/^[[:alnum:]][a-z0-9_.-]*@[a-z0-9.-]+\.[a-z]{2,4}$/i", $email)) {
        echo 'bad email';
    } else {
        echo 'good email';
    }
}

The reason your initial attempt didn't work is because it was trying to use ^ as the delimiter character but (obviously) found no matching ^ for the end of the regex.

edited Apr 28 '11 at 22:12

Peter Bailey

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answered Sep 03 '09 at 17:45

Amber

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Thanks, I just found php's FILTER_VALIDATE_EMAIL, it seems like it might be the best way to go but I cannot find much information on it – JasonDavis Sep 03 '09 at 17:47
2

@jasondavis, `FILTER_VALIDATE_EMAIL` would definitely be a better choice. E-mails are **complicated**. – TRiG Jun 27 '11 at 14:59

score 10 · Answer 2 · answered Sep 03 '09 at 17:49

10

You will need to change three things

need to add pattern delimiters (can be any character, but most commonly a forward slash)
[[:alnum:]] will need to be replaced with the PCRE equivalent
The "i" in "eregi" means case-insensitive, which PCRE does with a flag, specifically the i flag.

Otherwise, the rest looks PCRE compatible (yes, that's kind of redundant =P)

"/^[a-z0-9][a-z0-9_.-]*@[a-z0-9.-]+\.[a-z]{2,4}$/i"

answered Sep 03 '09 at 17:49

Peter Bailey

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1

PHP's PCRE includes things like [:alnum:] as options. – Amber Sep 03 '09 at 17:50

How to change PHP's eregi to preg_match

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