Help per una funzione

[badaze]

Prova questo.

$str = "1234[TOTO]4567[toto]7890[titi][IOPP]";
//---- il trucco
$str = "]".$str;

$pattern = "|[]](.*)[[]|U";

preg_match_all($pattern, $str , $matches);

print_r($matches); 

Array
(
    [0] => Array
        (
            [0] => ]1234[
            [1] => ]4567[
            [2] => ]7890[
            [3] => ][
        )

    [1] => Array
        (
            [0] => 1234
            [1] => 4567
            [2] => 7890
            [3] => 
        )

)