Normal function solution
//1,2,2,3,6,7,3,1,4,2
$arr=[
[1,2],
[2,3],
6,7,[3,1,[4,2]]
];
function a($array){
static $res=[];
foreach($array as $val){
if(is_array($val)){
a($val);
}else{
$res[]=$val;
}
}
return $res;
}
print_r(a($arr));