For first time learning
Like this array_multisort($arr1,$arr2,$arr3); The default is that all arrays are sorted in ascending order. If you want to sort $arr2 in descending order , and treated as strings for comparison, it must be written as:
array_multisort($arr1, $arr2, SORT_DESC, SORT_STRING, $arr3);
Each array can be followed by a sort order flag or a sort type flag, or both flags. But only one sort flag of each type can appear after each array.
PHP array_multisort sort order flags:
SORT_ASC - Sort in ascending order (default)
SORT_DESC - Sort in descending order
PHP array_multisort sort type flag:
SORT_REGULAR - compare items according to the usual method (default)
SORT_NUMERIC - compare items numerically
SORT_STRING - Compare items by string