how to use preg_replace for the following pattern

Question

Input: "abbbcdaa" Output: "abcd"

With the follow regex the out put is abcda

preg_replace('/(.)\\1*/', '$1', "abbbcdaa");

how to get abcd using pre_replace

Without regex: `echo implode("", array_unique(str_split($str)));` — bobble bubble, Nov 08 '15 at 05:35

angelcool.net · Answer 1 · 2015-11-08T05:52:57.163

0

This should do it:

$string="abbbcdaa";
echo preg_replace('/(.)(?=.*?\1)/','',$string);

The above outputs:

bcda

Alternatively, you can use:

echo count_chars($string,3);

That would also return unique characters abcd.

Good luck!

edited Nov 08 '15 at 05:52

answered Nov 08 '15 at 05:29

angelcool.net

Can you explain this part of regex (?=.*?\1) – Aditya Joshi Nov 08 '15 at 08:43
That's a look-ahead (google look-arounds). The entire regex will delete a char from the input string only if that char appears again later in the string. Also, take a look here: http://stackoverflow.com/questions/2582940/how-do-i-remove-duplicate-characters-and-keep-the-unique-one-only-in-perl – angelcool.net Nov 08 '15 at 17:11

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