matrix.php

<?php

function matrix($x = 3, $y = 3) {
	$_matrix = [];
	for($_x = 0; $_x < $x; $_x++) {
		for($_y = 0; $_y < $y; $_y++) {
			$_matrix[$_x][$_y] = mt_rand(1,5);
		}
	}
	return $_matrix;
}

function uniqMulti($arr) {
	$uniqs = [];
	foreach($arr as $row) {
		foreach($row as $key => $val) {
			if(!in_array($val, $uniqs)) {
			$uniqs[] = $val;
			}
		}
	}
	return $uniqs;
}

$matrix = matrix();

// матрица
print_r($matrix);
// уникальные значения
print_r(uniqMulti($matrix));