test test

{/c}
test test
{c} saddasda
{/c} {c}
test

{/c} {c}
{/c}'; $new_str = preg_replace_callback('#(?<=\{c\}).*?(?=\{/c\})#s', function($matches) { return str_replace("
", "[linebreak]", $matches[0]); },$str); echo $new_str;