PHP rsort() Function

The rsort() is an inbuilt function in PHP and is used to sort the array in descending order i.e, greatest to smallest. It sorts the actual array and hence changes are reflected in the array itself. The function provides us with 6 sorting types, according to which the array can be sorted. 

Syntax: 

rsort($array, sorting_type)

Parameters: 

1. $array: This parameter specifies the array which we want to sort.
2. sorting_type: This is an optional parameter. This parameter specifies the mode in which the sort operation will be performed on the input array. There are 6 sorting types which are described below: 
   
   • SORT_REGULAR - When we pass 0 or SORT_REGULAR in the sorting_type parameter, the items in the array are compared normally
   • SORT_NUMERIC - When we pass 1 or SORT_NUMERIC in the sorting_type parameter, the items in the array are compared numerically
   • SORT_STRING - When we pass 2 or SORT_STRING in the sorting_type parameter, the items in the array are compared string-wise
   • SORT_LOCALE_STRING - When we pass 3 or SORT_LOCALE_STRING in the sorting_type parameter, the items in the array are compared as string based on current locale
   • SORT_NATURAL - When we pass 4 or SORT_NATURAL in the sorting_type parameter, the items in the array are compared as string using natural ordering
   • SORT_FLAG_CASE - When we pass 5 or SORT_FLAG_CASE in the sorting_type parameter, the items in the array are compared as strings. The items are treated as case-insensitive and then compared. It can be used using | (bitwise operator) with SORT_NATURAL or SORT_STRING.

Return Value: It returns a boolean value, TRUE on success and False in failure. It sorts the original array in descending which is passed as a parameter to it. 

Examples: 

Input : $array = [3, 4, 1, 2] 
Output : 
Array
(
 [0] => 4
 [1] => 3
 [2] => 2
 [3] => 1
)


Input : $array = ["geeks2", "raj1", "striver3", "coding4"]
Output :
Array
(
 [0] => striver3 
 [1] => raj1 
 [2] => geeks2 
 [3] => coding4
)

Below programs illustrate the rsort() function in PHP:

Program 1: Program to demonstrate the use of rsort() function in descending order.  

Output: 

Array
(
 [0] => 4
 [1] => 3
 [2] => 2
 [3] => 1
)

Program 2: Program to demonstrate the use of rsort() function to sort the string case-sensitively in descending order. 

Output: 

Array
(
 [0] => striver
 [1] => Raj
 [2] => RAj
 [3] => geeks
 [4] => coding
)

Program 3 : Program to demonstrate the use of rsort() function to sort the string case-insensitively in descending order. 

Output: 

Array
(
 [0] => striver
 [1] => Raj
 [2] => RAj
 [3] => geeks
 [4] => coding
)

Reference: 
https://www.php.net/manual/en/function.rsort.php