Email validation with validation on username to accept only letters, digits, underscore and DOT

Question

I know this question asked many times but I could not find any solution to my specific validation.

I want to validate a username in email address to accept only letters, digits, underscore and DOT and NO dash (-) or any special character such as !#%&*()

Like this: [email protected], [email protected], [email protected], [email protected]

NOT like this: [email protected], [email protected], [email protected]

what i did:

if (!preg_match("/[a-zA-Z0-9]+@[a-zA-Z0-9]+.[a-zA-Z]+/", $email)) return("Invalid email address");

but it accepts dash.

possible duplicate of [How to validate an Email in PHP?](http://stackoverflow.com/questions/5855811/how-to-validate-an-email-in-php) — Phil Sturgeon, Apr 08 '15 at 16:24

anubhava · Accepted Answer · 2015-04-08T13:48:54.410

1

You can do:

if (!preg_match('/^(?!.*?\.\.)[\w.]+@(?:[a-zA-Z0-9-]+\.)+[a-zA-Z]+$/', $email)) 
    return("Invalid email address");

edited Apr 08 '15 at 13:48

answered Apr 08 '15 at 13:41

anubhava

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can i prevent double dot sequentially. like this [email protected] – Ayman Hussein Apr 08 '15 at 13:47
This will match `myemailª@test.com` – Pedro Lobito Apr 08 '15 at 13:53
1

@anubhava you're right, regexbuddy was giving me a false positive. sry about that. – Pedro Lobito Apr 08 '15 at 14:00

Pedro Lobito · Answer 2 · 2015-04-08T14:09:40.547

To prevent 2 consecutive dots (.) use negative lookahead (?!.*?\.\.)

if (!preg_match('/^(?!.*?\.\.)[a-z0-9_.]+@[a-z0-9.-]+\.[a-z]+$/im', $email))
    return("Invalid email address");

EXPLANATION:

^             # Assert position at the beginning of a line (at beginning of the string or after a line break character) (line feed)
(?!           # Assert that it is impossible to match the regex below starting at this position (negative lookahead)
   .             # Match any single character that is NOT a line break character (line feed)
      *?            # Between zero and unlimited times, as few times as possible, expanding as needed (lazy)
   \.            # Match the character “.” literally
   \.            # Match the character “.” literally
)
[a-z0-9_.]    # Match a single character present in the list below
                 # A character in the range between “a” and “z” (case insensitive)
                 # A character in the range between “0” and “9”
                 # A single character from the list “_.”
   +             # Between one and unlimited times, as many times as possible, giving back as needed (greedy)
@             # Match the character “@” literally
[A-Z0-9.-]    # Match a single character present in the list below
                 # A character in the range between “A” and “Z” (case insensitive)
                 # A character in the range between “0” and “9”
                 # The literal character “.”
                 # The literal character “-”
   +             # Between one and unlimited times, as many times as possible, giving back as needed (greedy)
\.            # Match the character “.” literally
[A-Z]         # Match a single character in the range between “A” and “Z” (case insensitive)
   +             # Between one and unlimited times, as many times as possible, giving back as needed (greedy)
\$             # Assert position at the end of a line (at the end of the string or before a line break character) (line feed)

Wiktor Stribiżew · Answer 3 · 2018-02-27T21:12:52.553

0

You can use the following regex that will also prevent 2 consecutive dots in the username:

^(?!.*\.\..*@)[a-zA-Z0-9_.]+@\S+\.[a-zA-Z]+$

See demo here.

Details

^ - start of string
(?!.*\.\..*@) - a negative lookahead that fails the match if there are two consecutive dots in the username part only
[a-zA-Z0-9_.]+ - one or more ASCII letters, digits or _ or .
@ - a @
\S+ - 1+ non-whitespace chars
\. - a dot
[a-zA-Z]+ - 1 or more ASCII letters
$ - end of string.

Sample code:

$re = "/^(?!.*\\.\\..*@)[a-zA-Z0-9_.]+@\\S+\\.[a-zA-Z]+$/m"; 
$str = "[email protected]\[email protected]\[email protected]\[email protected]\[email protected]"; 
preg_match($re, $str, $matches);

edited Feb 27 '18 at 21:12

answered Apr 08 '15 at 13:39

Wiktor Stribiżew

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got: Warning: preg_match(): No ending delimiter '^' found in – Ayman Hussein Apr 08 '15 at 13:41
Please check now, I included the "@..." part to the regex. – Wiktor Stribiżew Apr 08 '15 at 13:44
Please check my last regex version: the regex will prevent user from entering consecutive dots in the username, the TLD is matched using your own pattern. – Wiktor Stribiżew Apr 08 '15 at 14:32
@AymanHussein Please check my update, and note that anubhava's solution also fails the match if there are two consecutive dots in the domain part. – Wiktor Stribiżew Feb 27 '18 at 21:13

score -2 · Answer 4 · edited Apr 08 '15 at 15:51

-2

You can use this:

[\\w\\-\\+\\&\\*]+(?:\\.[\\w\\-\\_\\+\\&\\*]+)*@(?:[\\w-]+\\.)+[a-zA-Z]{2,7}

edited Apr 08 '15 at 15:51

ProgramFOX

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answered Apr 08 '15 at 13:46

lakshman

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Email validation with validation on username to accept only letters, digits, underscore and DOT

4 Answers4