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

Each entry in the associative array is characterized by a unique key-value pair. An array can contain singular data types belonging to variables or other arrays as its elements. There are multiple ways to sort an array of associative arrays by the value of a specified key. 

Approach 1: Using the array_multisort() method

The array_multisort() method is used to return a sorted array. String keys will be maintained, but the numeric keys are re-indexed, and they start at 0 and increase by 1. This function can sort multiple arrays at once or a multidimensional array. 

array_multisort(array, sort_order, sort_type);

Example: In this example, initially an array of associative arrays is defined. Then, a new array is created in order to store the keys as the attribute of the main array upon which we wish to sort. The array_multisort() method is then applied to this created array and the desired sort type. In case two or more keys are the same, the values appear in the order of storage. 

PHP

<?php
 #declaring an associative array
$arr = array(
   array("Name"=>"YASHIKA", "marks"=>22),
   array("Name"=>"ASHIKA", "marks"=>67),
   array("Name"=>"BASHIKA", "marks"=>87),
   array("Name"=>"YASHITA", "marks"=>24),
   array("Name"=>"AMAN", "marks"=>55),
   array("Name"=>"ANjali", "marks"=>98),
   array("Name"=>"YASHIKA", "marks"=>100),
);
#declaring an array to store names
$names = array();
#iterating over the arr
foreach ($arr as $key => $val)
{
  #storing the key of the names array as the Name key of the arr
    $names[$key] = $val['Name'];

}
#apply multisort method
array_multisort($names, SORT_ASC, $arr);
print_r("Modified Array : ");
print_r($arr);
?>

Output:

Modified Array : Array
(
    [0] => Array
        (
            [Name] => AMAN
            [marks] => 55
        )

    [1] => Array
        (
            [Name] => ANjali
            [marks] => 98
        )

    [2] => Array
        (
            [Name] => ASHIKA
            [marks] => 67
        )

    [3] => Array
        (
            [Name] => BASHIKA
            [marks] => 87
        )

    [4] => Array
        (
            [Name] => YASHIKA
            [marks] => 22
        )

    [5] => Array
        (
            [Name] => YASHIKA
            [marks] => 100
        )

    [6] => Array
        (
            [Name] => YASHITA
            [marks] => 24
        )
)

Explanation: The main array is sorted based on names in ascending order. 

Approach 2: Using the usort() method

This method sorts the given array using a user-defined comparison function. The user-defined function should return an integer <, =, or > than 0 if the first argument is <, =, or > than the second argument. This method assigns new keys to the elements in the array. It just removes any existing keys that may have been assigned, rather than just simply reordering the keys.

usort(array, user_def_func)

Example: This example uses the usort() method to sort an Array of Associative Arrays by the Value of a Given Key in PHP.

PHP

<?php
#sort in descending order
function DescSort($val1,$val2)
{
  #check if both the values are equal
    if ($val1['marks'] == $val2['marks']) return 0;
  #check if not equal, then compare values
    return ($val1['marks'] < $val2['marks']) ? 1 : -1;
}
#declaring an associative array
$arr = array(
   array("Name"=>"YASHIKA", "marks"=>22),
   array("Name"=>"ASHIKA", "marks"=>67),
   array("Name"=>"BASHIKA", "marks"=>87),
   array("Name"=>"YASHITA", "marks"=>24),
   array("Name"=>"AMAN", "marks"=>55),
   array("Name"=>"ANjali", "marks"=>98),
   array("Name"=>"YASHIKA", "marks"=>100),
);
#apply usort method on the array
usort($arr,'DescSort');
print_r("Modified Array : ");
print_r($arr);
?>

Output: The DescSort() method sorts the marks in descending order. 

Modified Array : Array
(
    [0] => Array
        (
            [Name] => YASHIKA
            [marks] => 100
        )

    [1] => Array
        (
            [Name] => ANjali
            [marks] => 98
        )

    [2] => Array
        (
            [Name] => BASHIKA
            [marks] => 87
        )

    [3] => Array
        (
            [Name] => ASHIKA
            [marks] => 67
        )

    [4] => Array
        (
            [Name] => AMAN
            [marks] => 55
        )

    [5] => Array
        (
            [Name] => YASHITA
            [marks] => 24
        )

    [6] => Array
        (
            [Name] => YASHIKA
            [marks] => 22
        )
)

Approach 3: Using the arsort() function

The arsort() in PHP is used to sort an array according to values. It sorts in a way that the relationship between indices and values is maintained. By default it sorts in descending order of values.

bool arsort( $array, $sorting_type )

Example: This example describes the use of the asort() function in order to sort the Array of Associative Arrays by Value for the Given Key in PHP.

PHP

<?php

# Declaring an associative array
$arr = array(
   array("Name"=>"YASHIKA", "marks"=>22),
   array("Name"=>"ASHIKA", "marks"=>67),
   array("Name"=>"BASHIKA", "marks"=>87),
   array("Name"=>"YASHITA", "marks"=>24),
   array("Name"=>"AMAN", "marks"=>55),
   array("Name"=>"ANjali", "marks"=>98),
   array("Name"=>"YASHIKA", "marks"=>100),
);

# Declaring an array to store marks
$marks = array();

# Iterating over the arr
foreach ($arr as $key => $val)
{
  # Storing the key of the marks array as
  # the marks key of the arr
    $marks[$key] = $val['marks'];

}
# Apply arsort method on the array
arsort($marks);
print_r("Modified Array : ");
print_r($marks);
?>

Output:

Modified Array : Array ( [6] => 100 
                         [5] => 98 
                         [2] => 87 
                         [1] => 67 
                         [4] => 55 
                         [3] => 24 
                         [0] => 22 )