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Collection of PHP array sorting functions and analysis of the connections between them_PHP Tutorial

WBOYOriginal: 2016-07-21 15:03:16819browse

The sorting of several array functions mentioned below have some commonalities:
1 The array is used as a parameter of the sorting function. After sorting, the array itself changes. The function The return value is of bool type.
2 The single a appearing in the function name means association, which means that in the process of sorting by value, the corresponding relationship of key=>value remains unchanged
3 The single k appearing in the function name means key, which means: , in the process of sorting by value, sort according to the array key instead of the value of the array
4 The single r appearing in the function name means reverse, which means that the order is in the opposite order of not adding r
5 Function name The single u appearing in means user-defined, which means that the user-defined function is used to sort. If the logic of the function is that parameter 1 < parameter 2 returns a negative number, then the order is in ascending order (p1 is smaller than 2 and returns negative and ascending).
--------------------sort function ascending order-------------------- ------------

Copy code The code is as follows:

bool sort ( array &$array [, int $sort_flags= SORT_REGULAR ] )
$fruits = array("lemon", "orange", "banana", "apple");
sort( $fruits);
var_dump($fruits);
?>
Result:
array
0 =>
string
'apple' (length=5)
1 =>
string
'banana' (length=6)
2 =>
string
'lemon' (length=5)
3 => ;
string
'orange' (length=6)

------------------------rsort descending order Arrangement--------------------

Copy code The code is as follows:

$fruits = array("lemon", "orange", "banana", "apple");
rsort($fruits);
var_dump($ fruits);
?>
Result: 
array
 0 => 
string
 'orange' (length=6)
 1 => string
 'lemon' (length=5)
 2 => 
string
 'banana' (length=6)
 3 => 
string
 'apple ' (length=5)

---------------asort is arranged in ascending order of the two-dimensional array values (keeping key=>value Association) -----------

Copy code The code is as follows:

< ;?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple" );
asort($fruits);
var_dump($fruits);
?>
Result: 
array
 'c' => 
string
 'apple' (length=5)
 'b' => 
string
 'banana' (length=6)
 'd' => 
string
 ' lemon' (length=5)
 'a' => 
string
 'orange' (length=6)

------ --arsort is arranged in descending order of the two-dimensional array values (maintaining the association of key=>value) ---------

Copy code The code is as follows:

$fruits = array("d" => "lemon", "a" => "orange", "b " => "banana", "c" => "apple");
arsort($fruits);
var_dump($fruits);
?>
result
 array
 'a' => 
string
 'orange' (length=6)
 'd' => 🎜> 'b' => 
string
 'banana' (length=6)
 'c' => 
string
 'apple' (length=5)
 


--------------------ksort sorts the array in ascending order of keys---------------- 

Copy code

The code is as follows:$fruits = array("d" =>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");

ksort($fruits);

 var_dump($fruits);
?>
result
array
'a' => 
string
 'orange' (length=6)
 'b' => 
string
 'banana' (length=6)
 'c' => 
string
 'apple' (length=5)
 'd' => ; 
string
 'lemon' (length=5)
 


------------------------krsort Arrange in descending order of array key-----------------------

Copy code

The code is as follows:

$fruits = array("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c "=>"apple");
krsort($fruits);
var_dump($fruits);
?>
array
 'd' => 
string 
 'lemon' (length=5)
 'c' => 
string
 'apple' (length=5)
 'b' => 
string
 'banana' (length=6)
 'a' => 
string
 'orange' (length=6)
 

----- ----------usort function sorts according to user-defined functions----------------

Copy code The code is as follows:

function cmp($a, $b)
{
 if ($a == $b) {
 return 0;
 }
 return ($a < $b) ? -1 : 1;
}
$a = array(3, 2, 5, 6, 1);
usort($a, "cmp");
var_dump($a);
?>

Result:
array
0 =>
int
1
1 =>
int
2
2 =>
int
5
4 =>
int
6

-----------------uksort use custom The function is sorted by the key of the array-----------------

Copy code

The code is as follows:function cmp($a, $b)

{
 $a = preg_replace('@^(a|an|the) @', ' ', $a);
 $b = preg_replace('@^(a|an|the) @', '', $b);
 return strcasecmp($a, $b);
 }
$a = array("John" => 1, "the Earth" => 2, "an apple" => 3, "a banana" => 4);
uksort( $a, "cmp");
var_dump($a);
?>


Result: 
array

'an apple' =>
int
3
'a banana' =>
int
4
'the Earth' =>
int
2
'John' => ;
int
1

--------------uasort uses a custom function to sort the array by value, keeping the index relationship unchanged----- ----

Copy code

The code is as follows:// Comparison function

function cmp($a, $b) {
 if ($a == $b) {
 return 0;
 }
 return ($a < $b) ? - 1 : 1;
}
// Array to be sorted
$array = array('a' => 4, 'b' => 8, 'c' => -1, 'd' => -9, 'e' => 2, 'f' => 5, 'g' => 3, 'h' => -4);
var_dump($array );
// Sort and print the resulting array
uasort($array, 'cmp');
var_dump($array);
?>


 Result: 
array

'a' =>
int
4
'b' =>
int
8
'c' =>
int
-1
'd' =>
int
-9
'e' =>
int
2
'f' = >
int
5
'g' =>;
int
3
'h' =>
int
-4
array
'd' =>
int
-9
'h' =>
int
-4
'c' =>
int
-1
'e' =>
int
2
'g' =>
int
3
'a' =>
int
4
'f' =>;
int
5
'b' =>;
int
8

------ -------------array_multisort Sort multiple arrays or multidimensional arrays---------

Copy code

The code is as follows:$ar = array(

array("10", 11, 100, 100, "a"),
array( 1, 2, "2", 3, 1)
);

array_multisort($ar[0], SORT_ASC, SORT_STRING,
$ar[1], SORT_NUMERIC, SORT_DESC) ;
var_dump($ar);
?>

Result:
array
0 =>
array
0 =>
string
'10' (length=2)
1 =>
int
100
2 =>
int
100
3 =>
int
11
4 =>
string
'a' (length=1)
1 =>
array
0 =>
int
1
1 =>
int
3
2 =>
string
'2' (length=1)
3 =>
int
2
4 =>
int
1
//Explanation:
1 In the above example: the $ar array is first sorted in ascending order according to the string value of $ar[0]. If the string values are equal, then the numbers in the $ar[1] array are sorted. Values are sorted in descending order.
2 If the parameter at any position of the array_multisort function is an array, it represents the value used for sorting.
If there are multiple array parameters, the previous array value will be sorted first. If it is a constant, such as
SORT_ASC, SORT_DESC, SORT_REGULAR,SORT_NUMERIC, SORT_STRING.
indicates the sorting method (array values are taken first).
================================================== ===========================================
PHP Two-dimensional array sorting function
PHP one-dimensional array can be sorted using functions such as sort(), asort(), arsort(), etc., but the sorting of PHP two-dimensional array needs to be customized.
The following function sorts a given two-dimensional array according to the specified key value. Let’s look at the function definition first:

Copy the code The code is as follows:

function array_sort($arr,$keys,$type='asc'){
$keysvalue = $new_array = array();
foreach ($arr as $k= >$v){
$keysvalue[$k] = $v[$keys];
}
if($type == 'asc'){
asort($keysvalue); 
}else{
arsort($keysvalue);
}
reset($keysvalue);
foreach ($keysvalue as $k=>$v){
$new_array [$k] = $arr[$k];
}
return $new_array;
}

It can sort the two-dimensional array according to the specified key value, You can also specify ascending or descending order (default is ascending order), usage example:

Copy code The code is as follows:

$ array = array(
array('name'=>'Mobile phone','brand'=>'Nokia','price'=>1050),
array('name'=>' laptop','brand'=>'lenovo','price'=>4300),
array('name'=>'razor','brand'=>'Philips', 'price'=>3100),
array('name'=>'Treadmill','brand'=>'Sanwa Soushi','price'=>4900),
array ('name'=>'Watch','brand'=>'Casio','price'=>960),
array('name'=>'LCD TV','brand'= >'Sony','price'=>6299),
array('name'=>'Laser Printer','brand'=>'HP','price'=>1200)
);
$ShoppingList = array_sort($array,'price');
print_r($ShoppingList);

The above is the two-dimensional array of $array according to 'price' 'Sort from low to high.
Output result: (omitted).

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