Question

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regexp to partly hide email?

I’m currently writing a script that hides an email address (so [e-mail] becomes t~~~@~~~~~~.com).

Whilst following the instructions on this question – regexp to partly hide email? – I have managed to get it to display t~~~@domain.com, but am having trouble removing the “domain”.

Here is what I have so far (assume $row->email is “[e-mail]”):-

$string = preg_replace("(?<=.).(?=.*@)","~", $row->email);
$string = preg_replace("(?<=@).[a-zA-Z0-9]*","~", $string);

However, all it returns is t~~~@~omain.com

I’m baffled as to how to get the rest of the domain bit. Ideas?

IDEALLY if anybody can provide a solution so it becomes t~~~@d~~~~~~.com, that’d be super.

Cheers

Answer 1

It is ..

• matching (and skipping) "@" and then;
• matching . (any character: i.e. the "d" in "domain") and then;
• matching 0 (zero) of the following character class, which is the minimum it needed to match the supplied regular expression.

That is, the first and only the first character after the @ was matched and replaced with ~.

The following

(?<=@.)[a-zA-Z0-9-]*(?=(?:[.]|$))

forces the character class to match to the first "." (period, as in ".com") or end-of-input.

Note that the . is moved inside of the (?<=@.)-look-behind clause which causes it to skip the first letter after the "@". I have also added a hyphen ("-") to the character class as they are valid (and not terribly uncommon) in domain names.

In addition, not all email addresses are in the trivial "a@b.c" form and Internationalized Domain Names (or IDN) can be represented locally in a non-punycode form when not transmitted (e.g. not used in a restricting context), but that is another topic. (It may be more appropriate to replace [a-zA-Z0-9-]* with [^.]* due to IDN without further specification.)