Here we will learn that how we can remove duplicate Array from multidimensional Array according to the key in the Array.
Lets look at the example below :-

Here I have initialized one multidimensional Array, now I would like to remove those Array which have same date time in Array like we can see here same dates are 2015-09-09 8:12:00 and 2015-12-10 10:12:00. So I will remove the duplicate Array which have same dates on the basis of key "date"

<?php

$array = array (
    array (
        "name" => "abc" ,
        "Age" => "25" ,
        "date" => "2015-09-09 8:12:00"
    ) ,
    array (
        "name" => "def" ,
        "Age" => "27" ,
        "date" => "2015-12-10 10:12:00"
    ) ,
    array (
        "name" => "abc" ,
        "Age" => "25" ,
        "date" => "2015-09-09 8:12:00"
    ) ,
    array (
        "name" => "jkl" ,
        "Age" => "22" ,
        "date" => "2015-09-11 12:12:00"
    ) ,
    array (
        "name" => "def" ,
        "Age" => "27" ,
        "date" => "2015-12-10 10:12:00"
    ) ,
);

echo "Original Array";
echo "<pre>";
print_r ( $array );
echo "</pre>";

function uniqueMultiArray ( $array , $key )
{
    $temp_array = $key_array = $duplicates = array ();
    $i = 0;

    foreach ( $array as $val )
    {
        if ( ! in_array ( $val[ $key ] , $key_array ) )
        {
            $key_array[ $i ] = $val[ $key ];
            $temp_array[ $i ] = $val;
        }
        else
        {
            $duplicates[] = $val[ $key ];
        }

        $i ++;
    }
    echo "Duplicate Array";
    echo "<pre>";
    print_r ( $duplicates );
    echo "</pre>";

    return $temp_array;
}

$newArray = uniqueMultiArray ( $array , "date" );
echo "New Array";
echo "<pre>";
print_r ( $newArray );
echo "</pre>";

Now run the code in your Browser , you will see the below output :-

Original Array
Array
(
    [0] => Array
        (
            [name] => abc
            [Age] => 25
            [date] => 2015-09-09 8:12:00
        )

    [1] => Array
        (
            [name] => def
            [Age] => 27
            [date] => 2015-12-10 10:12:00
        )

    [2] => Array
        (
            [name] => abc
            [Age] => 25
            [date] => 2015-09-09 8:12:00
        )

    [3] => Array
        (
            [name] => jkl
            [Age] => 22
            [date] => 2015-09-11 12:12:00
        )

    [4] => Array
        (
            [name] => def
            [Age] => 27
            [date] => 2015-12-10 10:12:00
        )

)
Duplicate Array
Array
(
    [0] => 2015-09-09 8:12:00
    [1] => 2015-12-10 10:12:00
)
New Array
Array
(
    [0] => Array
        (
            [name] => abc
            [Age] => 25
            [date] => 2015-09-09 8:12:00
        )

    [1] => Array
        (
            [name] => def
            [Age] => 27
            [date] => 2015-12-10 10:12:00
        )

    [3] => Array
        (
            [name] => jkl
            [Age] => 22
            [date] => 2015-09-11 12:12:00
        )

)

So Now here we can see original Array which I have initialized in the beginning, duplicates Array dates and New Array which have removed those two same dates Array Data.

Enjoy the Code ! :)