Please note, this is a STATIC archive of website www.w3resource.com from 19 Jul 2022, cach3.com does not collect or store any user information, there is no "phishing" involved.
w3resource

PHP Array Exercises : Sort an array according to another array as a priority list

PHP Array: Exercise-20 with Solution

Write a PHP function to sort an array according to another array acting as a priority list.

Sample Solution:

PHP Code:

<?php
function list_cmp($a, $b) 
{ 
  global $order; 

  foreach($order as $key => $value) 
    { 
      if($a==$value) 
        { 
          return 0; 
          break; 
        } 

      if($b==$value) 
        { 
          return 1; 
          break; 
        } 
    } 
} 

$order[0] = 1;
$order[1] = 3; 
$order[2] = 4; 
$order[3] = 2; 

$array[0] = 2;
$array[1] = 1; 
$array[2] = 3; 
$array[3] = 4; 
$array[4] = 2; 
$array[5] = 1; 
$array[6] = 2; 

usort($array, "list_cmp"); 

print_r($array); 
?>

Sample Output: 

Array                                                       
(                                                           
    [0] => 1                                                
    [1] => 1                                                
    [2] => 3                                                
    [3] => 4                                                
    [4] => 2                                                
    [5] => 2                                                
    [6] => 2                                                
)

Flowchart:

Flowchart: PHP - Sort an array according to another array as a priority list

PHP Code Editor:

Contribute your code and comments through Disqus.

Previous: Write a PHP script to print "second" and Red from the specified array.
Next: Write a PHP function to sort subnets.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



PHP: Tips of the Day

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC