Find identical elements in matrix rows?

Question

PHP

Good afternoon
There is such a task
There is a Matrix (exactly 4 rows, the length of the columns is unknown)
It is known that at least one row will not be empty, the rest may be empty
It is tedious to find the elements that are in all EXISTING rows ...

Answer 1

I don’t know if there are sets in php, but the algorithm is simple: the intersection of all lines is taken:

rows = [
    [1, 3, 4],
    [1, 2, 3, 5, 6],
    [1, 3, 5],
    [1, 3, 11]
]

res = set(rows[0])

for row in rows[1:]:
    res.intersection_update(row)

>>> {1, 3}

Answer 2

Unfortunately, I didn’t find anything as beautiful in php as in python (post above)
But here’s what I got, if anyone is interested

$a = array(
            array(1,2,4,5,6,7),
            array(2,5,7,1),
            array(1,2),
            array(1,'a','g',2),
        );
        $res = array();
        for($i=0; $i<count($a[0]); $i++){
            $flag = 0;
            for($j=1; $j<count($a); $j++){
                for($k=0; $k<count($a[$j]); $k++){
                    if($a[0][$i] == $a[$j][$k]){
                        $flag ++ ;
                        if($flag == 3){ array_push($res, $a[0][$i]); }
                    }
                } // k
            } // j
        } // for i
        print_r($res);