How to loop through a two dimensional array in PHP?

Question:

I have an array made up of array's and I don't know how to go through the values ​​of the internal arrays to do a check. Suppose that in an input I write "admin1" how can I go through the values ​​of the array.

$arrayRoles = array(
    array("admin1", "admin1", "administrador"),
    array("prof1", "prof1", "profesor"),
    array("alum1", "alum1", "alumno")
);

function checkUser($array, $usu) {
    for ($i = 0; $i < $array; $i++) {
        for ($i = 0; $i <=3; $i++){
        if $usu == 'valor de el array'{
                //Retorna true
            }
        }
    }
}

Answer:

$arrayRoles = array(
    array("admin1", "admin1", "administrador"),
    array("prof1", "prof1", "profesor"),
    array("alum1", "alum1", "alumno")
);

function checkUser($array, $usu) {
    for ($i = 0; $i < sizeof($array); $i++) {
        for ($j = 0; $j < sizeof($array[0]); $j++){
            if ($usu == $array[$i][$j]){
                return true;
            }
        }
    }
}