How to remove duplicate break lines with PHP

Question

I would like to know how could I remove duplicate break lines with PHP considering that the input can be from various OS.

Input Ex.: "02 02 02 02 \r\n\r\n 02 02 02 02 \r\n 02 02 02 02"

Input Ex.: "02 02 02 02 \n\n\n 02 02 02 02 \n\n 02 02 02 02"

Output Ex.: "02 02 02 02 \n 02 02 02 02 \n 02 02 02 02"

Answer 1

You could use preg_replace:

$s = preg_replace("/[\r\n]+/", "\n", $s);

See it working online: ideone

Answer 2

More quickly is to replace only 2+ line breaks :) :

$s = preg_replace("/([\r\n]{4,}|[\n]{2,}|[\r]{2,})/", "\n", $s);