Using regex for simple email validation [duplicate] - php

Question

This question already has answers here:
Closed 11 years ago.
Possible Duplicates:
What is the best regular expression for validating email addresses?
Is there a php library for email address validation?
On my register form a user will add his email and then get an email to verify his account. However I want to have a simple email validation and I would like to know if the following is appropriate.
<?php
$email = "someone#example.com";
if(eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*#[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $email)) {
echo "Valid email address.";
}
else {
echo "Invalid email address.";
}
?>

Answer 1

Try:
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
echo 'Valid';
} else {
echo 'Invalid';
}

Answer 2

Your regular expression unnecessarily forbids subdomains, such as user#unit.company.com. Additionally, you shouldn't use the deprecated eregi.
Instead of reinventing your own wheel, use filter_var:
if (filter_var($email, FILTER_VALIDATE_EMAIL)) {
echo "Valid email address.";
} else {
echo "Invalid email address.";
}

Answer 3

Apart from a regex, you can also use filter_var:
if (filter_var('someone#example.com', FILTER_VALIDATE_EMAIL)) === false)
{
echo "Invalid email address.";
}

Answer 4

Email validation is a bit tricky, because the RFC that specifies the format of email addresses is way more unrestrictive that people think. For example, the following are all valid email addresses:
"Abc#def"#example.com
"Fred Bloggs"#example.com
"Joe\Blow"#example.com
"Abc#def"#example.com
customer/department=shipping#example.com
$A12345#example.com
!def!xyz%abc#example.com
_somename#example.com
The correct regex for email validation seems to look something like this, which I won't even try to look into ;) However, when using PHP, you should really use filter_var(), like so:
$valid = filter_var($email, FILTER_VALIDATE_EMAIL);
# $valid will be TRUE if the email address was valid,
# otherwise FALSE.
RFC822 seems to contain the original email format specification, but I think that 2822 (as linked above) is just a revision / amendment of that original RFC.