How to write php array array function

There are many array sorting functions in PHP. Most of these functions can be parameterized by sorting (ascending or descending), sorting algorithm, and whether to retain the key values ​​​​of the array. Here are some of the most commonly used array sorting functions in PHP:

1. sort() function

sort() function can be used to sort the elements in an array in ascending order. This function changes the order of elements in the original array and returns a Boolean value indicating whether the sorting was successful.

For example, we can use the following code to sort the array $arr in ascending order:

$arr = array(5, 2, 8, 12);

sort($arr);

print_r($arr);

This will output: Array ( [0] => 2 [1] => 5 [2 ] => 8 [3] => 12 )

2. rsort() function

rsort() function can be used to sort the elements in the array in descending order . Like the sort() function, this function changes the order of elements in the original array and returns a Boolean value indicating whether the sorting was successful.

The following code uses the rsort() function to sort the array $arr in descending order:

$arr = array(5, 2, 8, 12);

rsort($arr);

print_r($arr);

This will output: Array ( [0] => 12 [1] => 8 [2 ] => 5 [3] => 2 )

3. asort() function

asort() function can be used to sort the values ​​in the array in ascending order , while retaining key values. Except for the sorting method, the other parameters of this function are the same as the sort() function.

The following code demonstrates the use of the asort() function:

$arr = array("b" => 5, "a" => 2, "d" => 8, "c" => 12);

asort($arr);

print_r($arr);

This will output: Array ( [a] => 2 [b] => 5 [d] => ; 8 [c] => 12 )

4. arsort() function

arsort() function can be used to sort the values ​​in the array in descending order while retaining key value. Except for the sorting method, the other parameters of this function are the same as the rsort() function.

The following code demonstrates the use of the arsort() function:

$arr = array("b" => 5, "a" => 2, "d" => 8, "c" => 12);

arsort($arr);

print_r($arr);

This will output: Array ( [c] => 12 [d] => 8 [b] => ; 5 [a] => 2 )

5. ksort() function

ksort() function can be used to sort the keys in an array in ascending order. Except for the sorting method, the other parameters of this function are the same as the sort() function.

The following code demonstrates the use of the ksort() function:

$arr = array("b" => 5, "a" => 2, "d" => 8, "c" => 12);

ksort($arr);

print_r($arr);

This will output: Array ( [a] => 2 [b] => 5 [c] => ; 12 [d] => 8 )

6. krsort() function

krsort() function can be used to sort the keys in the array in descending order. Except for the sorting method, the other parameters of this function are the same as the rsort() function.

The following code demonstrates the use of the krsort() function:

$arr = array("b" => 5, "a" => 2, "d" => 8, "c" => 12);

krsort($arr);

print_r($arr);

This will output: Array ( [d] => 8 [c] => 12 [b] => ; 5 [a] => 2 )

7. usort() function

usort() function can be used to customize the sorting of elements in an array. Custom sorting requires specifying a callback function that accepts two parameters and returns an integer value. If the specified callback function returns 1, it means that the first parameter is greater than the second parameter, and their positions are swapped when sorting; if -1 is returned, their positions are swapped. If the callback function returns 0, it means that the two parameters are equal and keep them in their original positions.

The following code demonstrates the use of usort() function and callback function:

$arr = array(5, 2, 8, 12);

usort($arr, function($a, $b) {
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
});

print_r($arr);

This will output: Array ( [0] => 2 [1] => 5 [2 ] => 8 [3] => 12 )

The above are some commonly used array sorting functions in PHP. They can handle different types of sorting requirements. We can choose which function to use according to specific needs.

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