Detailed explanation of array sorting function in PHP

PHP comes with a large number of array sorting functions. Let’s introduce the usage of PHP array sorting one by one.

The array is used as a parameter of the sorting function. After sorting, the array itself changes, and the return value of the function is of type bool.

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 a appearing in the function name means association. k represents key, which means that in the process of sorting by value, the array key is sorted instead of the value of the array

4 A single r appearing in the function name represents reverse, which means that the order is the opposite of that without r. The order of

5 The single u appearing in the function name means user-defined, which means that the user-defined function is used to sort. If the logic of the function is that parameter 1

--------------------sort function ascending order-------------------- ------------

代码如下

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

--------------------rsort in descending order------ ---------------

代码如下	复制代码
$fruits = array("lemon", "orange", "banana", "apple"); rsort($fruits); var_dump($fruits); ?> 结果： 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 the key =>value association) -----------

代码如下	复制代码
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple"); asort($fruits); var_dump($fruits); ?> 结果： 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)------------- -

The code is as follows

Copy code

代码如下

复制代码

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

--------------------ksort按照数组的key升序排列-------------- "lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");
ksort($fruits);
var_dump($fruits);
?>
结果
array
'a' => string 'orange' (length=6)
'b' => string 'banana' (length=6)
'c' => string 'apple' (length=5)
'd' => string 'lemon' (length=5)

$fruits = array("d" => "lemon", "a" => "orange", "b" => " banana", "c" => "apple");arsort($fruits);

代码如下

复制代码

$fruits = array("d"=>"lemon", "a"=>"orange", "b"=>"banana", "c"=>"apple");
krsort($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)

var_dump($fruits);

?>
result

array

代码如下

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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);
?>
结果：
array
0 => int 1
1 => int 2
2 => int 3
3 => int 5
4 => int 6

' a' => string 'orange' (length=6)

'd' => string 'lemon' (length=5)

'b' => string 'banana' (length=6)

代码如下

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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);
?>
结果：
array
'an apple' => int 3
'a banana' => int 4
'the Earth' => int 2
'John' => int 1

'c' => string 'apple' (length=5)--------------------ksort is in ascending order according to the key of the array Arrangement-------------- "lemon", "a"=>"orange", "b"=> "banana", "c"=>"apple");ksort($fruits);var_dump($fruits);?>resultarray 'a' => string 'orange' (length=6)'b' => string 'banana' (length=6)'c' => string 'apple' (length=5 )'d' => string 'lemon' (length=5)

------------- --------krsort sorts the array keys in descending order--------------------------------

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

---------------- The usort function is sorted according to user-defined functions----------------

The code is as follows	Copy code
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: array0 => int 11 => int 22 => int 33 => int 54 => int 6

-----------------uksort uses a custom function Sort by the key of the array-----------------

The code is as follows	Copy code
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---------

uasort($array, 'cmp'); var_dump($array);

The code is as follows

代码如下

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// 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);
?>
结果：
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

Copy code

代码如下

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$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);
?>
结果：
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

// 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

?>
Result: array

'a' => int 4

'a' => int 4'f' => int 5' b' => int 8

-------------------array_multisort Sort multiple arrays or multi-dimensional arrays- --------

The code is as follows

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$ar = array(<🎜>array("10", 11, 100, 100, "a"),<🎜> array( 1, 2, "2", 3, 1)<🎜>);<🎜><🎜>array_multisort($ar[0], SORT_ASC, SORT_STRING,<🎜>$ar[1], SORT_NUMERIC, SORT_DESC) ;<🎜>var_dump($ar);<🎜>?>Result: array0 => array0 => string '10' (length= 2)1 => int 1002 => int 1003 => int 114 => string 'a' (length=1)1 = > array0 => int 1 1 => int 32 => string '2' (length= 1)3 => int 24 => int 1//Explanation: 1 In the above example: the $ar array is prioritized in ascending order according to the string value of $ar[0] Arrange, if the string values are equal, then sort according to the numeric value of the $ar[1] array 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). http://www.bkjia.com/PHPjc/444669.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/444669.htmlTechArticle PHP comes with a large number of array sorting functions. Let’s introduce one by one about PHP array sorting. How to use it. The array is used as a parameter of the sorting function. After sorting, the array itself...

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Detailed explanation of array sorting function in PHP_PHP tutorial