How to Sort an Array of Associative Arrays by Value of a Given Key in PHP

  1. Use array_multisort() Function to Sort an Array of Associative Arrays by the Value of a Given Key in PHP
  2. Use the usort() Function to Sort an Array of Associative Arrays by the Value of a Given Key in PHP

This article will introduce methods to sort an array of associative arrays by the value of a given key in PHP.

  • Using array_multisort() function
  • Using usort() function

Use array_multisort() Function to Sort an Array of Associative Arrays by the Value of a Given Key in PHP

We can use the built-in function array_multisort() to sort an array of associative arrays by the value of a given key. It can sort many arrays at a time or a multidimensional array. The correct syntax to use this function is as follows

str_replace($arrayName, $sort_order, $sort_flags);

The built-in function array_multisort() has three parameters. The details of its parameters are as follows

Parameters Description
$arrayName mandatory It is the array that we want to sort.
$sort_order optional It specifies the order in which we will sort our array. It can be SORT_ASC for ascending order and SORT_DESC for descending order. Its default value is SORT_ASC.
$sort_flags optional It specifies the options for sorting. You can read it here.

This function returns TRUE if it is successful. Otherwise, it returns FALSE.

The program below shows how we can use the array_multisort() function to sort an array of associative arrays by the value of a given key.

<?php 
$result = array(

   array("firstname"=>"Olivia", "marks"=>85),
   array("firstname"=>"Jacob", "marks"=>60),
   array("firstname"=>"Henry", "marks"=>100),
   array("firstname"=>"Lili", "marks"=>40),
   array("firstname"=>"Stefan", "marks"=>5),
   array("firstname"=>"Bonnie", "marks"=>97),
);
$marks = array();
foreach ($result as $key => $row)
{
    $marks[$key] = $row['marks'];
    
}
array_multisort($marks, SORT_DESC, $result);
print_r($result);  
?> 

We have created an array $marks containing the marks from the original array. After that, we have used the array_multisort() function to sort $marks array based on the $result array. The output will be the $result array sorted.

Output:

Array
(
    [0] => Array
        (
            [firstname] => Henry
            [marks] => 100
        )

    [1] => Array
        (
            [firstname] => Bonnie
            [marks] => 97
        )

    [2] => Array
        (
            [firstname] => Olivia
            [marks] => 85
        )

    [3] => Array
        (
            [firstname] => Jacob
            [marks] => 60
        )

    [4] => Array
        (
            [firstname] => Lili
            [marks] => 40
        )

    [5] => Array
        (
            [firstname] => Stefan
            [marks] => 5
        )

)

The array is sorted in descending order by the value of the marks key.

Use the usort() Function to Sort an Array of Associative Arrays by the Value of a Given Key in PHP

In PHP, we can also use the usort() function to sort an array of associative arrays by the value of a given key. This function sorts the array using a user-defined function. The correct syntax to use this function is as follows:

preg_replace($arrayName, $functionName);

The function the usort() accepts two parameters. The detail of its parameters is as follows

Parameters Description
$arrayName mandatory It is the array that we want to sort
$functionName mandatory It is the user-defined function that will sort the passed array.

It returns TRUE if successful, FALSE otherwise. The program that sorts the array is as follows:

<?php 
function DescSort($item1,$item2)
{
    if ($item1['marks'] == $item2['marks']) return 0;
    return ($item1['marks'] < $item2['marks']) ? 1 : -1;
}
$result = array(

   array("firstname"=>"Olivia", "marks"=>85),
   array("firstname"=>"Jacob", "marks"=>60),
   array("firstname"=>"Henry", "marks"=>100),
   array("firstname"=>"Lili", "marks"=>40),
   array("firstname"=>"Stefan", "marks"=>5),
   array("firstname"=>"Bonnie", "marks"=>97),
);
usort($result,'DescSort');
print_r($result);
?> 

Output:

Array
(
    [0] => Array
        (
            [firstname] => Henry
            [marks] => 100
        )

    [1] => Array
        (
            [firstname] => Bonnie
            [marks] => 97
        )

    [2] => Array
        (
            [firstname] => Olivia
            [marks] => 85
        )

    [3] => Array
        (
            [firstname] => Jacob
            [marks] => 60
        )

    [4] => Array
        (
            [firstname] => Lili
            [marks] => 40
        )

    [5] => Array
        (
            [firstname] => Stefan
            [marks] => 5
        )

)

For ascending sort, the function will be:

<?php 
function AscSort($item1,$item2)
{
    if ($item1['marks'] == $item2['marks']) return 0;
    return ($item1['marks'] > $item2['marks']) ? 1 : -1;
}
$result = array(

   array("firstname"=>"Olivia", "marks"=>85),
   array("firstname"=>"Jacob", "marks"=>60),
   array("firstname"=>"Henry", "marks"=>100),
   array("firstname"=>"Lili", "marks"=>40),
   array("firstname"=>"Stefan", "marks"=>5),
   array("firstname"=>"Bonnie", "marks"=>97),
);
usort($result,'AscSort');
print_r($result);
?> 

Output:

Array
(
    [0] => Array
        (
            [firstname] => Stefan
            [marks] => 5
        )

    [1] => Array
        (
            [firstname] => Lili
            [marks] => 40
        )

    [2] => Array
        (
            [firstname] => Jacob
            [marks] => 60
        )

    [3] => Array
        (
            [firstname] => Olivia
            [marks] => 85
        )

    [4] => Array
        (
            [firstname] => Bonnie
            [marks] => 97
        )

    [5] => Array
        (
            [firstname] => Henry
            [marks] => 100
        )

)

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