Double array in foreach loop

Question

I am modifying a php function. there is foreach loop which is annoying for me. below is the source code

$array_a = array(
 //value here.
);
$array_b = array(
 //value here.
)
foreach ( $array_a + $array_b as $key => $query ) {
 unset( $meta_key[ $key ] ); //or whatever
}

Question

$array_a + $array_b

why they are using two arrays & i think there is an increment operator between them. i want to know the logic and reason of doing that?

Answer 1

The + operator appends elements of remaining keys from the right handed array to the left handed, whereas duplicated keys are NOT overwritten. With the foreach loop basically he is going through the array keys and values,