How to replace unmatched words with special character?

Question

I want to replace equal number of unmatched characters with *. Like as I've string

xyzdsdasdas@xyss.com

should be replace into

x*********s@x**s.com

Right now just for work around I'm using the following regex

^(\w).*?(.@.).*?(.\.\w+)

So using that followed regex along with preg_replace like as

echo preg_replace('/^(\w).*?(.@).*?(\.\w+)/', "$1****$2****$3", "xyzdsdasdas@xyss.com");

which result into

x****s@x****s.com

but what I want to achieve over here is

x*********s@x**s.com

Demo

Downvoters please post the reason for downvoting the question — , Oct 02 '15 at 09:31
may be you should try a loop with "for" instead of preg_replace — Mimouni, Oct 02 '15 at 09:33
Maybe preg_replace (and regexp at all) is not the more efficient way to achieve this. — Amessihel, Oct 02 '15 at 09:37
first explode two part with "@", get the count of first part replace chars with * from 2 to n-1; with the second part replace chars with * from 2 to n-5, this is not very inteligent solution but still work — Mimouni, Oct 02 '15 at 09:41
@Amessihel really? check my answer. It would be much more efficient than explode. — Avinash Raj, Oct 02 '15 at 09:46
@AvinashRaj I didn't mean to use explode instead. :) But your answer rocks. — Amessihel, Oct 02 '15 at 09:58

Avinash Raj · Accepted Answer · 2015-10-02T09:51:50.733

3

I would use (*SKIP)(*F)

preg_replace('~(?:^.|.@.|.\.\w+$)(*SKIP)(*F)|.~', '*', $str);

DEMO

First match all the chars you don't want. ie, (?:^.|.@.|.\.\w+$)
Now, skip those matches using (*SKIP)(*F)
| OR
Now the dot after | will match all the characters other than the skipped ones.

edited Oct 02 '15 at 09:51

answered Oct 02 '15 at 09:44

Avinash Raj

172,303
28
230
274

Its working fine but I didn't understand `(*SKIP)(*F)|.` part of the regex – Oct 02 '15 at 09:50
1

Great Explanation. @Avi +1 – Narendrasingh Sisodia Oct 02 '15 at 09:52
@Avinash Raj, I've learnt something today. `(*SKIP)` and `(*F)` are PCRE control-verb patterns which modify the behaviour of the engine. Once a pattern is matched, `(*SKIP*)` tells the engine to "skip" to the next position once the first try of matching succeeded. Then `(*F)` - aka `(*FAIL)` - will tell the engine to act as if the matching failed, in order to retry pattern matching at the current position. More infos [here](http://stackoverflow.com/a/24535912/4375327). Official PERL doc [here](http://perldoc.perl.org/perlre.html). – Amessihel Oct 02 '15 at 12:06
Another interesting point : is here `preg_replace` more optimized than a couple of str_replace ? – Amessihel Oct 02 '15 at 12:08

score 0 · Answer 2 · answered Oct 02 '15 at 09:44

Not using preg_replace, just to give you an idea, my code is not optimized ! (I know)

$str = 'xyzdsdasdas@xyss.com';
$buff = explode('@', $str);
$buff2 = explode('.', $buff[1]);

$part1 = $buff[0][0] . str_repeat('*', strlen($buff[0]) - 2) . $buff[0][strlen($buff[0]) - 1];
$part2 = $buff[1][0] . str_repeat('*', strlen($buff2[0]) - 2) . $buff2[0][strlen($buff2[0]) - 1];

echo $part1 .'@'. $part2 .'.'. $buff2[1];

But it works.

score 0 · Answer 3 · answered Oct 02 '15 at 09:55

Also you can use preg_replace_callback function

function callbackFunction($m) {
  return $m[1].(str_repeat('*', strlen($m[2]))).$m[3].(str_repeat('*', strlen($m[4]))).$m[5];
}

$pattern = '|^(\\w)(.*?)(.@.)(.*?)(.\\.\\w+)|';
$subject = 'xyzdsdasdas@xyss.com';
print_r( preg_replace_callback($pattern, 'callbackFunction', $subject, -1 ) );

score 0 · Answer 4 · answered Oct 02 '15 at 09:55

Another try, without explode :

<?php

$email="blablabla@truc.com" ;

$arobase_pos = strpos($email,"@"); // first occurence of "@"
$dot_pos = strrpos($email,".");    // last occurence of ".""

// from 2 to post(@) -1
$email = substr_replace($email, str_repeat ("*", $arobase_pos - 2), 1, $arobase_pos - 2);
// from pos(@)+2 to pos(.)-1 
$email = substr_replace($email, str_repeat ("*", $dot_pos-1-$arobase_pos-2),  $arobase_pos + 2, $dot_pos-1-$arobase_pos-2);

// Display
echo $email;
?>

How to replace unmatched words with special character?

4 Answers4