PHP multidimensional Array custom sort Uasort ()

PHP has a lot of built-in sorting functions, pros and cons of various rows;

Commonly used sorting functions:

Sort ()-sorts an array in ascending order
Rsort ()-sorts the array in descending order
Asort ()-sorts associative arrays in ascending order based on values
Ksort ()-Sorts the associative array in ascending order, based on the key
Arsort ()-sorts associative arrays in descending order by value
Krsort ()-Sorts the associative array in descending order, based on the key

Basic can meet the needs of the use of these functions are not more verbose;

But in the actual development of the project there will be some more demanding sorting requirements; the sort function to be introduced today is: Uasort ()

Uasort is mainly used in the order of the multidimensional arrays that need to follow the custom method and keep the index relationship ;

Has the following array

$sort _array = array (     "Array1"  => array (          ' word ' = ' test1 ',         ' Sortnumber ' =>1,     ),     ' Array3 ' =>array (          ' word ' = ' test4 ',         ' Sortnumber ' =>4,     ),     ' array2 ' =>array (         ' word ' ~ = ' test3 ',         ' Sortnumber ' =>3,    ),      ' Array5 ' =>array (         ' word ' = ' test5 ',     ),     ' Array4 ' =>array (          ' word ' = ' test2 ',         ' Sortnumber ' =>2,     ),);

The requirements are sorted in ascending order according to Sortnumber;

First, you need to write a custom sort rule;

Custom sort functions Function My_sort ($a, $b) {$prev = isset ($a [' sortnumber '])? $a [' Sortnumber ']: 0; $next = Isset ($b [' Sortnumber '])?    $b [' Sortnumber ']: 0;    if ($prev = = $next) return 0; Return ($prev < $next)? -1:1;} Echo ' <pre> sort before:<br> ';p rint_r ($sort _array); Uasort ($sort _array, "My_sort"); echo "Sort:<br>";p Rint_ R ($sort _array);

The results obtained:

Before sorting: Array (    [array1] => Array          (            [word] => test1             [sortnumber] => 1         )     [array3] => Array          (            [ Word] => test4            [sortnumber ] => 4        )     [array2] = > Array         (             [word] => test3             [sortnumber] => 3        )     [array5]  => array         (             [word] => test5        )     [array4] => Array         (             [word] => test2             [sortnumber] => 2         )) After sorting: Array (    [array5] => Array          (            [ word] => test5        )     [array1]  => array         (             [word] => test1            [ sortnumber] => 1        )     [array4]  => Array         (             [word] => test2             [sortnumber] => 2        )     [array2] => Array         (             [word] => test3             [sortnumber] => 3         )     [array3] => Array         (             [word] => test4             [sortnumber] => 4         ))

The last to be reminded is: the custom function to use isset detection under the need to sort the existence of the field if there is no default 0 assigned to, otherwise there will be an error message;

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PHP multidimensional Array custom sort Uasort ()