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Which PHP function(s) should I use to sort an associative array by its key or value?

1 Answer

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There are 4 different PHP functions to sort an associative array by key/value in ascending/descending order.

  1. asort(): Sort by value in ascending order.
  2. arsort(): Sort by value in descending order.
  3. ksort(): Sort by key in ascending order.
  4. krsort(): Sort by key in descending order.
Here is an example to show these functions:

    <?php
    // sort by key in ascending order
    print("\nSort by key in ascending order:\n");
    $arr1 = array("cat"=>53, "banana"=>11, "apple"=>24, "egg"=>9, "dog"=>42, "fat"=>55, "hat"=>12, "goat"=>37 );
    ksort($arr1);
    foreach($arr1 as $k=>$v){
        echo $k . "=>" . $v;
        echo "\n";
    }

    // sort by key in desceding order
    print("\nSort by key in desceding order:\n");
    $arr1 = array("cat"=>53, "banana"=>11, "apple"=>24, "egg"=>9, "dog"=>42, "fat"=>55, "hat"=>12, "goat"=>37 );
    krsort($arr1);
    foreach($arr1 as $k=>$v){
        echo $k . "=>" . $v;
        echo "\n";
    }

    // sort by value in ascending order
    print("\nSort by value in ascending order:\n");
    $arr1 = array("cat"=>53, "banana"=>11, "apple"=>24, "egg"=>9, "dog"=>42, "fat"=>55, "hat"=>12, "goat"=>37 );
    asort($arr1);
    foreach($arr1 as $k=>$v){
        echo $k . "=>" . $v;
        echo "\n";
    }

    // sort by value in desceding order
    print("\nSort by value in desceding order:\n");
    $arr1 = array("cat"=>53, "banana"=>11, "apple"=>24, "egg"=>9, "dog"=>42, "fat"=>55, "hat"=>12, "goat"=>37 );
    arsort($arr1);
    foreach($arr1 as $k=>$v){
        echo $k . "=>" . $v;
        echo "\n";
    }

    ?>
The output of the above code is as follows:   
Sort by key in ascending order:
    apple=>24
    banana=>11
    cat=>53
    dog=>42
    egg=>9
    fat=>55
    goat=>37
    hat=>12

    Sort by key in desceding order:
    hat=>12
    goat=>37
    fat=>55
    egg=>9
    dog=>42
    cat=>53
    banana=>11
    apple=>24

    Sort by value in ascending order:
    egg=>9
    banana=>11
    hat=>12
    apple=>24
    goat=>37
    dog=>42
    cat=>53
    fat=>55

    Sort by value in desceding order:
    fat=>55
    cat=>53
    dog=>42
    goat=>37
    apple=>24
    hat=>12
    banana=>11
    egg=>9
...