$re = '/(?:[a-z0-9!#$%&\'*+\/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&\'*+\/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])/m';
$str = 'Valid email addresses
simple@example.com
"user@name"@example.com
very.common@example.com
disposable.style.email.with+symbol@example.com
other.email-with-hyphen@example.com
fully-qualified-domain@example.com
user.name+tag+sorting@example.com (may go to user.name@example.com inbox depending on mail server)
x@example.com (one-letter local-part)
example-indeed@strange-example.com
test/test@test.com (slashes are a printable character, and allowed)
admin@mailserver1 (local domain name with no TLD, although ICANN highly discourages dotless email addresses[10])
example@s.example (see the List of Internet top-level domains)
" "@example.org (space between the quotes)
"john..doe"@example.org (quoted double dot)
mailhost!username@example.org (bangified host route used for uucp mailers)
user%example.com@example.org (% escaped mail route to user@example.com via example.org)
user-@example.org (local part ending with non-alphanumeric character from the list of allowed printable characters)
postmaster@[123.123.123.123] (IP addresses are allowed instead of domains when in square brackets, but strongly discouraged)
postmaster@[IPv6:2001:0db8:85a3:0000:0000:8a2e:0370:7334] (IPv6 uses a different syntax)
Invalid email addresses
Abc.example.com (no @ character)
A@b@c@example.com (only one @ is allowed outside quotation marks)
a"b(c)d,e:f;gi[j\\k]l@example.com (none of the special characters in this local-part are allowed outside quotation marks)
just"not"right@example.com (quoted strings must be dot separated or the only element making up the local-part)
this is"not\\allowed@example.com (spaces, quotes, and backslashes may only exist when within quoted strings and preceded by a backslash)
this\\ still\\"not\\\\allowed@example.com (even if escaped (preceded by a backslash), spaces, quotes, and backslashes must still be contained by quotes)
1234567890123456789012345678901234567890123456789012345678901234+x@example.com (local-part is longer than 64 characters)
i_like_underscore@but_its_not_allowed_in_this_part.example.com (Underscore is not allowed in domain part)
QA[icon]CHOCOLATE[icon]@test.com (icon characters)';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php