How to get array key with less than values - php

Question

I have 2 arrays:
$arr_1=array(200, 300, 200, 200);
$arr_2=array(
1 => array(70, 90, 70, 20),
2 => array(115, 150, 115, 35),
3 => array(205, 250, 195, 55),
4 => array(325, 420, 325, 95),
5 => array(545, 700, 545, 155)
);
Now I need some way to get array keys for arrays in $arr_1 where all their values are less than all values from $arr_2.
In the above example it must return key 1 AND key 2 from $arr_2 without using a foreach loop.

Answer 1

You can use array_filter to filter the elements (it preserves keys) and then pass the result to array_keys to receive an array of keys.
Also, your condition can be spelled this way: "return subarrays from $arr_2 where highest value is smaller than smallest value of $arr_1."
$arr_1=array(200, 300, 200, 200);
$arr_2=array(
1 => array(70, 90, 70, 20),
2 => array(115, 150, 115, 35),
3 => array(205, 250, 195, 55),
4 => array(325, 420, 325, 95),
5 => array(545, 700, 545, 155)
);
$filtered = array_filter($arr_2, function($value) use ($arr_1) {
return max($value) < min($arr_1);
});
$keys = array_keys($filtered);
var_dump($keys);

Answer 2

If you are only interested in comparing the subarrays against the lowest value in $arr_1, then best practices dictates that you declare that value before entering the array_filter(). This will spare the function having to call min() on each iteration. (Demo)
$arr_1=[200,300,200,200];
$arr_2=[
1=>[70,90,70,20],
2=>[115,150,115,35],
3=>[205,250,195,55],
4=>[325,420,325,95],
5=>[545,700,545,155]
];
$limit=min($arr_1); // cache this value, so that min() isn't called on each iteration in array_filter()
$qualifying_keys=array_keys(array_filter($arr_2,function($a)use($limit){return max($a)<$limit;}));
var_export($qualifying_keys);
/*
array(
0=>1,
1=>2,
)
*/