preg_replace search for string that does not match the pattern instead of string that match the pattern

Question

I have this array of possible values that I want to replace with preg_replace function:

$attr = array('b','i','u','left','center','right');

foreach($attr as $a) {
    // strip bbcode
    $str = preg_replace('#\['.$a.'\](.*)\[/'.$a.'\]#im','$1',$str); 
}
return $str;

but instead of using foreach and looping through each possible exclusion, I want to do it like strip anything that isn't an img instead. Is this possible?

Answer 1

Do you mean you want to strip out all tags except img tags? Use this:

$str = preg_replace('#\[(?!/?img).+?]#im','',$str);