Summary of common array sorting methods in PHP

1. Simple array sortingsort() Function and rsort() Function:

Grammar rules:

bool sort(array &array [,int sort_flags]
bool rsort(array &array [.int_sort_flags]

Parameters:

The first parameter is a sorted array object

The second parameter is an optional value that can be selected:

SORT_REGULAR: It is the default value and will automatically Identify the element type of the array for sorting
SORT_NUMERIC: used for sorting array elements
SORT_STRING: used for string sorting
SORT_LOCALE_STRING: Compare elements as strings according to the current locale setting

Example:

$a=array(4,7,9,1);
sort($a);
pirnt_r($a);
rsort($a);
print_r($a);

2. Sort the array according to the key name

Definition: ksort() The function sorts the array from small to large according to the key name. krsort()Contrary to the ksort() function, the original keys are maintained for the array values ​​after sorting.

Example

$data= array(5=>"five",8=>"eight",1=>"one",7=>"seven");
ksrot($data);
print_r($data);
krsot($data);
print_r($data);

3. Sort according to element value

Definition: asort() From small to large/ arsort() From large to small, use this function to sort, the original key name will be ignored, use the sequential number to re-index the array subscript

Example:

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

4. Natural sorting

Definition : is a very special sorting method that uses cognition instead of calculation rules. This feature is called natural sorting method, that is, numbers from 1 to 9, letters from a-z, and the shorter one is given priority.

Example:

$data=array("file1.txt","file11.txt","file111.txt");
natsort($data);//普通自然排序
natcasesort($data);//忽略大小写

5. According to user-defined sorting rules

Grammar rules:

bool usort(array &array ,callback cmp_function)
bool uasort(array &array,callback cmp_function)
bool uksort(array &array,callback cmp_function)

Description: Custom callback function requires two parameters , respectively two consecutive elements of the array. Comparing the first parameter is less than, greater than, and equal to the second parameter returns 0, 1, -1 respectively

Example:

$data= array("ab","abc","a","ac","abcd");
usrot($data,"mysortByLen");
function mysortByLen($one,$two){
 if(strlen($one)== strlen($two)){
  return 0;
 }else{
 return (strlen($one)>strlen($two))?1:-1;
}

6. Multidimensional Array sorting

Definition: array_multisort()The function sorts multiple arrays, or sorts multi-dimensional arrays according to a certain dimension or multiple dimensions.

bool array_multisort(array array1 [,mixed arg,[,array ....]])

Example:

$data=array(
  array("id"=>1,"name"=>4),
  array("id"=>1,"name"=>2),
  array("id"=>2,"name"=>3)
);
foreach($data as $key=>$value){
 $ids[$key]=$value["id"];
 $names[$key]=$value["name"]
}
array_multisort($data,$ids,$names);
print_r($data);

Output result:

array(    array("id"=>1,"name"=>2),    array("id"=>1,"name"=>4),    array("id"=>2,"name"=>3)
 );

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