Sort a multidimensional array by date element in PHP

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Sorting a multidimensional array by element containing date. Use the usort() function to sort the array. The usort() function is PHP builtin function that sorts a given array using user-defined comparison function. This function assigns new integral keys starting from zero to array elements.

Syntax:

boolean usort( $array, "function_name")

Parameters: This function accepts two parameters as shown in the above syntax and are described below:

$array: This parameter specifies the array which u want to sort.
function_name: This parameter specifies the name of a user-defined function which compares the values and sort the array specified by the parameter $array. This function returns an integer value based on the following conditions. If two argument are equal then it returns 0, If first argument is greater than second, it returns 1 and if first argument is smaller than second, it returns -1.

Return Value: This function returns Boolean type value. It returns TRUE in case of success and FALSE in case of failure.

We use strtotime to convert given time string to a timestamp object. Once we have timestamps, we subtract them to decide greater.

Program:

<?php 
  
// Declare a multidimensional array 
// and initialize it 
$array = Array ( 
    Array ( 
        "gfg" => "GFG_1", 
        "datetime" => "2019-02-22 11:29:45", 
        ), 
    Array ( 
        "gfg" => "GFG_2", 
        "datetime" => "2019-02-13 11:29:45", 
    ), 
    Array ( 
        "gfg" => "GFG_3", 
        "datetime" => "2019-02-15 11:29:45", 
    ) 
); 
  
// Comparison function 
function date_compare($element1, $element2) { 
    $datetime1 = strtotime($element1['datetime']); 
    $datetime2 = strtotime($element2['datetime']); 
    return $datetime1 - $datetime2; 
}  
  
// Sort the array  
usort($array, 'date_compare'); 
  
// Print the array 
print_r($array) 
  
?> 

Output:

Array
(
    [0] => Array
        (
            [gfg] => GFG_2
            [datetime] => 2019-02-13 11:29:45
        )

    [1] => Array
        (
            [gfg] => GFG_3
            [datetime] => 2019-02-15 11:29:45
        )

    [2] => Array
        (
            [gfg] => GFG_1
            [datetime] => 2019-02-22 11:29:45
        )

)