Notes on using PHParray_multisort () functions

Array_multisort sorts multiple arrays or multi-dimensional arrays. For more information, see. Function bool array_multisort (array & $ arr [, mixed $ arg = SORT_ASC [, mixed $ arg = SORT_REGULAR [, mixed $...])
Parameter description: The function sorts multiple arrays or multi-dimensional arrays.
The first parameter is an array, and each subsequent parameter may be an array or the following sort order mark.
SORT_ASC-default, in ascending order
SORT_DESC-sort in descending order
You can specify the sorting type.
SORT_REGULAR-default. Sort each item in the general order.
SORT_NUMERIC-sort each item in numerical order.
SORT_STRING-sort each item in alphabetical order.
Instance code
The code is as follows:
$ Arr1 = array ('10', 11,100,100, 'A ');
$ Arr2 = array (1, 2, 3, '2', 5 );
Array_multisort ($ arr1, $ arr2 );

Result:
$ Arr1
Array ([0] => 10 [1] => a [2] => 11 [3] => 100 [4] => 100)
# '10' is converted to an integer 10 when compared with 11,100,100, which is smaller than the other three.
# '10' is a string when 'A' is compared. Its first character '1' ascii code value is 49 less than 'A' (ascii value is 97 ), therefore, '10' is the minimum element.
# When 'A' is compared with the other three numbers, it is converted to an integer 0, which is smaller than the other three.
$ Arr2
Array ([0] => 1 [1] => 5 [2] => 2 [3] => 2 [4] => 3)
# $ Arr2 element 1 corresponds to $ arr1 element '10', so it is in the [0] position.
# $ Arr1 [2] => 100, $ arr1 [3] => 100 corresponds to $ arr2 element 3, '2' respectively '. 3 is greater than '2'. Therefore, the subscript corresponding to $ arr1 [2] => 100 after sorting is
3. the subscript of $ arr1 [3] => 100 sorting is 4.
Summary
1. the number of elements in the array to be sorted must be consistent.
2. the position of the elements in the sorting array corresponds to, for example, '10' => 1, 11 => 2.
3. the back array is sorted based on the order of the front array.
4. in case of equal elements, the array of the front edge compares the array

Array_multisort-sorts multiple arrays or multi-dimensional arrays.

Description
Bool array_multisort (array $ ar1 [, mixed $ arg [, mixed $... [, array $...])
Returns TRUE if the call succeeds, or FALSE if the call fails.

Array_multisort () can be used to sort multiple arrays at a time, or to sort multi-dimensional arrays based on one or more dimensions.

The association (string) key name remains unchanged, but the number key name is re-indexed.

The input array is treated as a table column and ordered BY rows-similar to the SQL ORDER BY clause. The first array is the main array to be sorted. If the rows (values) in the array are the same, they are sorted by the corresponding values in the next input array.

The parameter structure of this function is somewhat unusual, but flexible. The first parameter must be an array. Each of the following parameters can be an array or a sorting marker listed below.

Sort order mark:

SORT_ASC-sort by ascending order
SORT_DESC-sort by descent

Sorting type flag:

SORT_REGULAR-compare projects by common methods
SORT_NUMERIC-compare projects by numerical values
SORT_STRING-compare items by string

You cannot specify two Sorting flags of the same type after each array. The sorting flag specified after each array is only valid for this array-the default values are SORT_ASC and SORT_REGULAR.

#1 sort multiple arrays
The code is as follows:
$ Ar1 = array ("ten", 100,100, "");
$ Ar2 = array (1, 3, "2", 1 );
Array_multisort ($ ar1, $ ar2 );
Var_dump ($ ar1 );
Var_dump ($ ar2 );
?>

In this example, after sorting, the first array will contain "10", "a", 100,100. The second array will contain 1, 1, "2", 3. The project order in the second array is exactly the same as that in the first array (100 and 100.
The code is as follows:
Array (4 ){
[0] => string (2) "10"
[1] => string (1) ""
[2] => int (100)
[3] => int (100)
}
Array (4 ){
[0] => int (1)
[1] => int (1)
[2] => string (1) "2"
[3] => int (3)
}

#2 sort multidimensional arrays
The code is as follows:
$ Ar = array ("10", 100,100, "a"), array (1, 3, "2", 1 ));
Array_multisort ($ ar [0], SORT_ASC, SORT_STRING,
$ Ar [1], SORT_NUMERIC, SORT_DESC );
?>

In this example, after sorting, the first array will contain 10,100,100, "a" (as the string ascending order), and the second array will contain 1, 3, "2 ", 1 (sort the values in descending order ).

#3 Sorting multi-dimen1_array
The code is as follows:
$ Ar = array (
Array ("10", 11,100,100, ""),
Array (1, 2, "2", 3, 1)
);
Array_multisort ($ ar [0], SORT_ASC, SORT_STRING,
$ Ar [1], SORT_NUMERIC, SORT_DESC );
Var_dump ($ ar );
?>

In this example, after sorting, the first array will become "10", 100,100, 11, "a" (sorted in ascending order as strings ). The second array will contain 1, 3, "2", 2, 1 (arranged in descending order as numbers ).
The code is as follows:
Array (2 ){
[0] => array (5 ){
[0] => string (2) "10"
[1] => int (100)
[2] => int (100)
[3] => int (11)
[4] => string (1) ""
}
[1] => array (5 ){
[0] => int (1)
[1] => int (3)
[2] => string (1) "2"
[3] => int (2)
[4] => int (1)
}
}

#4 sort database results
In this example, each unit in the data array represents a row in a table. This is a collection of typical database records.

The data in the example is as follows:

Volume | edition
------- + --------
67 | 2
86 | 1
85 | 6
98 | 2
86 | 6
67 | 7

All data is stored in an array named data. This is usually the result obtained from the database through a loop, such as mysql_fetch_assoc ().

$ Data [] = array ('Volume '=> 67, 'version' => 2 );
$ Data [] = array ('Volume '=> 86, 'version' => 1 );
$ Data [] = array ('Volume '=> 85, 'version' => 6 );
$ Data [] = array ('Volume '=> 98, 'version' => 2 );
$ Data [] = array ('Volume '=> 86, 'version' => 6 );
$ Data [] = array ('Volume '=> 67, 'version' => 7 );
?>
In this example, we will sort volume in descending order and edition in ascending order.

Now we have an array containing rows, but array_multisort () needs an array containing columns. Therefore, we use the following code to obtain and sort columns.

// Retrieve the column list
Foreach ($ data as $ key => $ row ){
$ Volume [$ key] = $ row ['Volume '];
$ Edition [$ key] = $ row ['version'];
}

// Sort data by volume in descending order and edition in ascending order
// Use $ data as the last parameter and sort it by a common key
Array_multisort ($ volume, SORT_DESC, $ edition, SORT_ASC, $ data );
?>
The data set is sorted as follows:

Volume | edition
------- + --------
98 | 2
86 | 1
86 | 6
85 | 6
67 | 2
67 | 7


Example #5 sorting case-insensitive letters

Both SORT_STRING and SORT_REGULAR are case-sensitive letters. uppercase letters are placed before lowercase letters.

To sort the data in case-insensitive order, the data is sorted by copying the lowercase letters of the original array.
The code is as follows:
$ Array = array ('alpha', 'Atomic ', 'beta', 'bank ');
$ Array_lowercase = array_map ('strlower ', $ array );

Array_multisort ($ array_lowercase, SORT_ASC, SORT_STRING, $ array );

Print_r ($ array );
?>

The above routine will output:

Array
(
[0] => Alpha
[1] => atomic
[2] => bank
[3] => Beta
)

[Note] This function is quite useful. to help you understand it, let's look at the following example:


Example #6 ranking
The code is as follows:
$ Grade = array ("score" => array (70, 95, 70.0, 60, "70 "),
"Name" => array ("Zhang San", "Li Si", "Wang Wu ",
"Zhao Liu", "Liu Qi "));
Array_multisort ($ grade ["score"], SORT_NUMERIC, SORT_DESC,
// Take the score as a value, sorted from high to low
$ Grade ["name"], SORT_STRING, SORT_ASC );
// Use the name as a string in ascending order
Var_dump ($ grade );
?>

The above routine will output:

Array (2 ){
["Score"] =>
Array (5 ){
[0] =>
Int (95)
[1] =>
String (2) "70"
[2] =>
Float (70)
[3] =>
Int (70)
[4] =>
Int (60)
}
["Name"] =>
Array (5 ){
[0] =>
String (5) "Li Si"
[1] =>
String (6) "Liu Qi"
[2] =>
String (7) "Wang Wu"
[3] =>
String (9) "Zhang San"
[4] =>
String (8) "Zhao Liu"
}
}
In this example, the $ grade array containing scores is sorted by score from high to low, and those with the same scores are sorted by name from small to large. After sorting, Li Si 95 is ranked first, while Zhao liu60 is ranked fifth without objection. Zhang San, Wang Wu, and Liu Qi both scored 70 points. their rankings were alphabetically arranged by their names. Liu was in the front, Wang was in the back, and Zhang was in the end. For the difference, the three 70-minute values are represented by integers, floating-point numbers, and strings. The Sorting results can be clearly seen in the program output.