Let's talk about the built-in sorting method of PHP arrays

In PHP, array is a very commonly used data type. For array processing, sorting is a very important operation. In PHP, there are many built-in sorting functions. This article will introduce the built-in sorting method of PHP array.

1. sort()

The sort() function is used to sort an array in ascending order. The specific syntax is:

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

Among them, $array represents the array that needs to be sorted, and $sort_flags represents the sorting rule. By default, sorting is in ascending order. The $sort_flags optional parameter has the following types:

• SORT_REGULAR - the default sorting rule, each value is compared in the usual way.
• SORT_NUMERIC - Sort by numerical value.
• SORT_STRING - Sort strings lexicographically.
• SORT_LOCALE_STRING - Sort strings lexicographically according to the current localization settings.
• SORT_NATURAL - Sort by natural number sequence. For example, "a1" comes before "10".
• SORT_FLAG_CASE - Can be used with any of the previous collation rules to treat the upper and lower case of string letters as different.

Example:

$arr ​​= array("apple", "banana", "grape");
sort($arr);
print_r($ arr);

Output result:

Array ( [0] => apple [1] => banana [2] => grape )

2. rsort()

The rsort() function is very similar to the sort() function, except that it sorts the array in descending order. The specific syntax is:

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

Example:

$arr ​​= array("apple", "banana", "grape");
rsort($arr);
print_r($arr);

Output result:

Array ( [0] => grape [1] => banana [2] => apple )

3. asort()

asort() function sorts the array in ascending order and retains The original key name. The specific syntax is:

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

Example:

$arr ​​= array("b" = > 2, "a" => 1, "c" => 3);
asort($arr);
print_r($arr);

Output result:

Array ( [a] => 1 [b] => 2 [c] => 3 )

4. arsort()

arsort The () function is very similar to the asort() function, except that it sorts the array in descending order. The specific syntax is:

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

Example:

$arr ​​= array("b" = > 2, "a" => 1, "c" => 3);
arsort($arr);
print_r($arr);

Output result:

Array ([c] => 3 [b] => 2 [a] => 1 )

5. ksort()

ksort () function sorts the array in ascending order by key name. The specific syntax is:

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

Example:

$arr ​​= array("b" = > 2, "a" => 1, "c" => 3);
ksort($arr);
print_r($arr);

Output result:

Array ( [a] => 1 [b] => 2 [c] => 3 )

6. krsort()

krsort The () function is very similar to the ksort() function, except that it sorts the array in descending order of key names. The specific syntax is:

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

Example:

$arr ​​= array("b" = > 2, "a" => 1, "c" => 3);
krsort($arr);
print_r($arr);

Output result:

Array ([c] => 3 [b] => 2 [a] => 1 )

7. usort()

usort The () function is used to customize the sorting of the array, that is, sorting according to the rules defined by yourself. The specific syntax is:

usort(array &$array, callable $function): bool

Among them, $array represents the array that needs to be sorted, and $function represents the function used to compare array elements. The function needs to return an integer when comparing, representing the comparison result of the two values.

Example:

$arr ​​= array(3, 5, 1, 4, 2);
usort($arr, function($a, $b) {

if ($a == $b) return 0;
return ($a < $b) ? -1 : 1;

});
print_r($arr);

Output result:

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

8. uasort()

uasort() function is very similar to usort() function Similar, except it retains the original key names. The specific syntax is:

uasort(array &$array, callable $function): bool

Example:

$arr ​​= array("b" => 2, "a" => 1, "c" => 3);
uasort($arr, function($a, $b) {

if ($a == $b) return 0;
return ($a < $b) ? -1 : 1;

});
print_r($ arr);

Output result:

Array ( [a] => 1 [b] => 2 [c] => 3 )

9. uksort()

uksort() function sorts the key names of the array according to custom rules. The specific syntax is:

uksort(array &$array, callable $function): bool

Among them, $array represents the array that needs to be sorted, and $function represents the function used to compare array key names. The function needs to return an integer when comparing, representing the comparison result of the two key names.

Example:

$arr ​​= array("b" => 2, "a" => 1, "c" => 3);
uksort($ arr, function($a, $b) {

if ($a == $b) return 0;
return ($a < $b) ? -1 : 1;

});
print_r($arr);

Output result:

Array ([a] => 1 [b] => 2 [c] => 3 )

Summary:

In PHP, there are a variety of sorting functions to choose from. According to different needs, choosing different sorting methods can allow us to operate arrays more efficiently.

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