Question

I am using regex function to get the email address from the string. The email address is inside the string covered both side with different characters like.

string=:'Here is the email address I would like to get out of here [e-mail] in 1 st try'

This following syntax returns email address but miss the Capital characters and returns email address from about string like [[e-mail]] capital A is missed.

$regex='`([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})`';

Answer 1

I didn’t check your regex in detail, but if the capital characters are the only problem, then just add the i modifier after the last regex delimiter

$regex='`([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})`i';

this modifier makes the regex match case insensitive.

OK, then you should add at least some anchors \b to the regex, to avoid partial matches.

$regex='`\b([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,6})\b`i';

See it here on Regexr

The \b matches on a change from a word character (A-Za-z0-9_) to a non-word character (all the others) and the other way round.

You should think about changing the last quantifier from {2,4} to {2,6}, there are some rare domains that are longer than 4 characters.