how review twin arrays mislay relating elements unbroken loop?

how else competence review twin arrays ($a $b )and devaluate relating elements out initial prep unbroken loop over array $a?

$a = array(1,2,3,4,5,6,7,8);
$b = array(1,2,3,4);

$c = array_intersect($a,$b);  //equals (1,2,3,4)
$a = array_diff($a,$b);       //equals (5,6,7,8)

is simplest proceed there proceed another duty i haven't guess of? idea have an array i loop over, pulling out groups associated calm (i have tangible those family elsewhere) until array advantage false.