Wrong negative look behind expression?

Question

I'm trying to filter every string which are not valid (simple) email adress. Thus starting with a dot is a "no go".

But my expression doesn't reject strings like .test@test.be

preg_match('/^(?<!\.)[\w0-9\.]+(?<!\.)@+(?<!\.)[\w0-9\.]+\.\w{1,3}(\s*<[^>]+>)?$/', $part)

Shouldn't /^(?<!\.) do the trick?

EDIT: This question is not a duplicate of the indicated question.

I am not asking about the context, I want more information about look behind, the approach itself, not the specific use-case.

Have you looked at `filter_var()` with filter `FILTER_VALIDATE_EMAIL`? — Jasper N. Brouwer, Jun 10 '15 at 10:04

Dmitry Egorov · Answer 1 · 2015-06-10T10:12:19.323

0

It turns out its look-ahead counterpart (^(?!\.)) does the trick instead: https://regex101.com/r/zZ8yT7/1

edited Jun 10 '15 at 10:12

answered Jun 10 '15 at 10:05

Dmitry Egorov

could it be that look behind expression are meant to be put at the end of something instead of in front of it? – Serge Profafilecebook Jun 10 '15 at 13:23

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