php email validation not recognizing .com.com - php

Question

Given below is the test code for the issue
If an invalid email with extension .com.com is given it is treated as valid
Please help to resolve the same
Thanks in advance
<?php
if(isset($_POST['submit']))
{
function validate_email($email)
{
$exp = "^[a-z\'0-9]+([._-][a-z\'0-9]+)*#([a-z0-9]+([._-][a-z0-9]+))+$";
if(eregi($exp,$email))
{
if(checkdnsrr(array_pop(explode("#",$email)),"MX"))
{
return 1;
}
else
{
return 0;
}
}
else
{
return 0;
}
}
$email = $_POST['email'];
print $details= validate_email($email);
}
?>
<form action="" method="post">
<h1> Email </h1>
<input type="email" name="email">
<button type="submit" name="submit"> SUBMIT </button>
</form>

Answer 1

How should it know that that email address is wrong?
A valid email address is already "someone#company"
Where "company" could be your intranet systems hostname. For reasons like that FILTER_VALIDATE_EMAIL doesn't check for a "valid" TLD, as it could not know if it is valid.
As for that it is recommended to NOT write a more specific check on your own, as in a lot of scenarios those checks could render your application useless.

Answer 2

You can use
$pattern = "/^[_a-z0-9-]+(\.[_a-z0-9-]+)*#[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,})$/i";
or Just
filter_var('email#email',FILTER_VALIDATE_EMAIL)

Answer 3

You can use this regex :
^([a-z\'0-9\._-]+)#([a-z0-9]+)((\.[a-z0-9]{2,3})(\.[a-z0-9]{2})|(\.[a-z0-9]{2,3}))$
Working well with "john.doe#gmail.com" or "john.doe#domain.co.uk", but it's very difficult to match all the possibilities now too many different tld are availables.
You should try the API of an email verification service.
Regards