How to sort arrays in PHP

In PHP, array is a very commonly used data type. When we need to sort the elements in the array, PHP provides some very convenient sorting functions, namely sort, rsort, asort, arsort, ksort, krsort, etc.

1. sort

The sort function is a function that sorts the array elements from small to large and retains the index relationship. Its syntax is as follows:

bool sort ( array &$array [, int $sort_flags = SORT_REGULAR ] )

Among them, $array represents the array to be sorted, and the $sort_flags parameter represents other sorting methods and can be omitted.

Example:

$arr = array(4,3,6,7,2,8,1);
sort($arr);
print_r($arr);

Output:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 6
    [5] => 7
    [6] => 8
)

2. rsort

The rsort function is the opposite function of the sort function and is based on the array A function that sorts the values ​​of elements from large to small and retains the index relationship. Its syntax is as follows:

bool rsort ( array &$array [, int $sort_flags = SORT_REGULAR ] )

Among them, $array represents the array to be sorted, and the $sort_flags parameter represents other sorting methods and can be omitted.

Example:

$arr = array(4,3,6,7,2,8,1);
rsort($arr);
print_r($arr);

Output:

Array
(
    [0] => 8
    [1] => 7
    [2] => 6
    [3] => 4
    [4] => 3
    [5] => 2
    [6] => 1
)

3. asort

The asort function sorts the array elements according to their values ​​from small to large. The syntax of a function that retains key-value relationships is as follows:

bool asort ( array &$array [, int $sort_flags = SORT_REGULAR ] )

Among them, $array represents the array to be sorted, and the $sort_flags parameter represents other sorting methods and can be omitted.

Example:

$arr = array("a"=>4,"f"=>3,"c"=>6,"d"=>7,"b"=>2,"e"=>8,"g"=>1);
asort($arr);
print_r($arr);

Output:

Array
(
    [g] => 1
    [b] => 2
    [f] => 3
    [a] => 4
    [c] => 6
    [d] => 7
    [e] => 8
)

4. arsort

The arsort function is the opposite function of the asort function and is based on the array A function that sorts the values ​​of elements from large to small and retains key-value relationships. Its syntax is as follows:

bool arsort ( array &$array [, int $sort_flags = SORT_REGULAR ] )

Among them, $array represents the array to be sorted, and the $sort_flags parameter represents other sorting methods and can be omitted.

Example:

$arr = array("a"=>4,"f"=>3,"c"=>6,"d"=>7,"b"=>2,"e"=>8,"g"=>1);
arsort($arr);
print_r($arr);

Output:

Array
(
    [e] => 8
    [d] => 7
    [c] => 6
    [a] => 4
    [f] => 3
    [b] => 2
    [g] => 1
)

5. ksort

The ksort function sorts the array key names from small to large, and The syntax of a function that retains key-value relationships is as follows:

bool ksort ( array &$array [, int $sort_flags = SORT_REGULAR ] )

Among them, $array represents the array to be sorted, and the $sort_flags parameter represents other sorting methods and can be omitted.

Example:

$arr = array("a"=>4,"f"=>3,"c"=>6,"d"=>7,"b"=>2,"e"=>8,"g"=>1);
ksort($arr);
print_r($arr);

Output:

Array
(
    [a] => 4
    [b] => 2
    [c] => 6
    [d] => 7
    [e] => 8
    [f] => 3
    [g] => 1
)

6. krsort

The krsort function is the opposite function of the ksort function and is based on the array The function that sorts the key names from large to small and retains the key-value relationship has the following syntax:

bool krsort ( array &$array [, int $sort_flags = SORT_REGULAR ] )

Among them, $array represents the array to be sorted, and the $sort_flags parameter represents other sorting methods and can be omitted.

Example:

$arr = array("a"=>4,"f"=>3,"c"=>6,"d"=>7,"b"=>2,"e"=>8,"g"=>1);
krsort($arr);
print_r($arr);

Output:

Array
(
    [g] => 1
    [f] => 3
    [e] => 8
    [d] => 7
    [c] => 6
    [b] => 2
    [a] => 4
)

Summary

In this article, we introduced 6 commonly used array sorting functions in PHP, namely sort, rsort, asort, arsort, ksort, krsort. These functions are very convenient and easy to use. Through these functions, we can easily sort arrays in PHP.

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