PHP array_intersect

array_intersect and array_intersect_key

array_intersect compares only values.

array_intersect_key compares only keys.

array_uintersect compares only values with a compare function.

array_intersect_ukey compares only keys with a compare function.

array_intersect_assoc

array_intersect_assoc compares keys and values.

array_intersect_uassoc compares keys and values with a key comparison function.

array_uintersect_assoc compares keys and values with a value comparison function.

array_uintersect_uassoc compares keys and values with a value comparison function and a key comparison function.

meaning of u

When intersect is prefixed with u, it means a value comparison function.

When key or assoc is prefixed with u, it means a key comparison function.

two u’s

When there are two u’s, first callback is for intersect, second callback is for assoc. This is exactly the order they appear in the function name.

array_diff

Same applies to array_diff.