Question

$arr1 = array(
  'a' => 123,
  'b' => 123,
  'c' => 123,
  'd' => 123,
);

$arr2 = ('a', 'b', 'c', 'd', 'e');

How can I remove elements from $arr2 that don’t exist as keys in $arr1 ?

for example e doesn’t exist as key in $arr1 so it should be removed

Answer 1

$arr2 = array_intersect($arr2, array_keys($arr1))

it computes intersection of two sets – $arr2 values and $arr1 keys