Validate email address with multi level domains in PHP with RegEx

Question

Need to validate email address with single domain level or multi level domains.(actually domain level <=4)

Criteria:

Email (username) should start with letter[a-z] and it may have numbers but not for 1st letter and periods(.) No other characters.
After @ sign every domain should start with letter.(minimum length 2)
Maximum domains <= 4 .

Ex: [email protected]

above example there 4 domains;

.my
.sub
.mail
.com

I try with this RegEx:

^[a-zA-Z](:?[a-zA-Z0-9._-])+(@[a-zA-Z]+[a-zA-Z0-9_-])+\.+(([a-zA-Z]){2,6})$

But above regex not validating multiple domains correctly.It's only get 1 domain. Ex: [email protected]

Online Regex : https://regex101.com/r/7SXS1Z/1

Try ^[a-zA-Z][a-zA-Z0-9._-]+@(?:[a-zA-Z][a-zA-Z0-9_-]+\.){1,4}[a-zA-Z]{2,6}$ — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Jun 26, 2017 at 17:58
I've done this one filter_var($s_email, FILTER_SANITIZE_EMAIL); — Elshan
– Elshan, Commented Jun 26, 2017 at 18:04
@AbraCadaver I need to validate something like this-> [email protected] so if I used FILTER_VALIDATE_EMAIL itself it's says above email also valid technically. — Elshan
– Elshan, Commented Jun 26, 2017 at 18:17
Because that is a valid email, so you only want to accept certain valid emails... — AbraCadaver
– AbraCadaver, Commented Jun 26, 2017 at 18:21

revo · Accepted Answer · 2017-06-26 17:59:38Z

1

Your regex applies much more rules in accepting an email address. E.g. allowing email addresses to include more than one @ symbol. Go as simple as your own rules:

^[a-z][^@]*@(([a-z][a-z0-9-]+)\.){0,3}(?2)$

Live demo

answered Jun 26, 2017 at 17:59

revo

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4 Comments

Elshan Over a year ago

Can you explain this part [^@]*@

revo Over a year ago

Yes, it means any character except a @ up to a @.

AbraCadaver Over a year ago

Need i modifier if you're not using A-Z

revo Over a year ago

It wasn't significant to note but I have set it in live demo already. @AbraCadaver

Jan · Accepted Answer · 2017-06-26 18:30:08Z

1

Maybe this is what you're looking for

^
[a-zA-Z][-.\w]*       # before @
@
[a-zA-Z][-.\w]+       # first subdomain
(?:
    \.[a-zA-Z][-.\w]+ # eventually others
){1,3}
$

See a demo on regex101.com.

edited Jun 26, 2017 at 18:30

answered Jun 26, 2017 at 18:05

Jan

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1 Comment

revo Over a year ago

You are ignoring email addresses with dots . and dashes - in user/domain names.

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