Best email validation function in general and specific (college domain)?

I know email validation is one of those things which is not the funniest thing on the block. I'm starting up a website and i want to limit my audience to only the people in my college and i also want a preferred email address for my user. So this is a two part question.

1. Is there a really solid php function out there for email validation?

2. Can I validate an email from a specific domain. I dont want to just check if the domain exists, because I know www.my开发者_开发问答college.edu exists already. Is there really anyway to validate that the user has a valid @mycollege.edu web address?

This is what I use:

   function check_email_address($email) {
        // First, we check that there's one @ symbol, and that the lengths are right
        if (!preg_match("/^[^@]{1,64}@[^@]{1,255}$/", $email)) {
            // Email invalid because wrong number of characters in one section, or wrong number of @ symbols.
            return false;
        }
        // Split it into sections to make life easier
        $email_array = explode("@", $email);
        $local_array = explode(".", $email_array[0]);
        for ($i = 0; $i < sizeof($local_array); $i++) {
            if (!preg_match("/^(([A-Za-z0-9!#$%&'*+\/=?^_`{|}~-][A-Za-z0-9!#$%&'*+\/=?^_`{|}~\.-]{0,63})|(\"[^(\\|\")]{0,62}\"))$/", $local_array[$i])) {
                return false;
            }
        }
        if (!preg_match("/^\[?[0-9\.]+\]?$/", $email_array[1])) { // Check if domain is IP. If not, it should be valid domain name
            $domain_array = explode(".", $email_array[1]);
            if (sizeof($domain_array) < 2) {
                return false; // Not enough parts to domain
            }
            for ($i = 0; $i < sizeof($domain_array); $i++) {
                if (!preg_match("/^(([A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9])|([A-Za-z0-9]+))$/", $domain_array[$i])) {
                    return false;
                }
            }
        }

        return true;
    }

EDIT Replaced depreciated ereg with preg_match for PHP 5.3 compliance

If you really want to make sure its valid make your signup form send them an email with a URL link in that they have to click to validate.

This way not only do you know the address is valid (because the received the email), but you also know the owner of the account has signed up (unless someone else knows his login details).

To make sure it ends correctly you could use explode() on the '@' and check the second part.

$arr = explode('@', $email_address);
if ($arr[1] == 'mycollege.edu')
{
    // Then it's from your college
}

PHP also has it's own way of validating email addresses using filter_var: http://www.w3schools.com/php/filter_validate_email.asp

This should work:

if (preg_match('/^([a-zA-Z0-9])+([a-zA-Z0-9\._-])@mycollege.edu$/', $email)) {
     // Valid
}

Read here http://ru2.php.net/manual/en/book.filter.php

Or in short

var_dump(filter_var('bob@example.com', FILTER_VALIDATE_EMAIL));

this might be a better solution. many answered already, eventhough its little different.

$email = "info@stakoverflow.com";

if (!filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
 echo $email ." is a valid email address";
} else {
  echo $email ." is not a valid email address";
}

I hope this one has simple to use.

for any e-mail

([a-zA-Z0-9_-]+)(\@)([a-zA-Z0-9_-]+)(\.)([a-zA-Z0-9]{2,4})(\.[a-zA-Z0-9]{2,4})?

for php preg_match function

/([a-zA-Z0-9_-]+)(\@)([a-zA-Z0-9_-]+)(\.)([a-zA-Z0-9]{2,4})(\.[a-zA-Z0-9]{2,4})?/i

for @mycollege.edu

^([a-zA-Z0-9_-]+)(@mycollege.edu)$

for php preg_match function

/^([a-zA-Z0-9_-]+)(@mycollege.edu)$/i

PHP CODE

<?php 

$email = 'tahir_aS-adov@mycollege.edu';
preg_match('/^([a-zA-Z0-9_-]+)(@mycollege.edu)$/i', $email, $matches);

if ($matches) { 
    echo "Matched";
} else {
    echo "Not Matched";
}

var_dump($matches);

A simple function using filter_var in php

<?php
function email_validation($email) {
    if (!filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
       echo("$email is a valid email address");
    } else {
       echo("$email is not a valid email address");
    }
}

//Test
email_validation('johnson123');
?>