How to Efficiently Deduplicate a PHP Multi-Dimensional Array Based on a Specific Key?

PHP Multi-Dimensional Array: Deduplicating Based on a Specific Value

Question:

Given a multi-dimensional array, how do you efficiently remove sub-arrays containing duplicate values for a particular key?

Problem Statement:

Consider the following multi-dimensional array:

Array
(
[0] => Array
    (
        [0] => dave
        [1] => jones
        [2] => [email protected]
    )

[1] => Array
    (
        [0] => john
        [1] => jones
        [2] => [email protected]

    )

[2] => Array
    (
        [0] => bruce
        [1] => finkle
        [2] => [email protected]
    )
)

The task is to remove any sub-arrays where the email address (index 2) appears more than once. In this example, it would result in removing either the first or third sub-array.

Solution:

A straightforward solution involves using array uniqueness to eliminate duplicate email addresses:

$newArr = array();
foreach ($array as $val) {
    $newArr[$val[2]] = $val;    
}
$array = array_values($newArr);

This solution leverages the fact that array keys in PHP are unique. By using the email address as the array key, it ensures that only the last occurrence of a particular email address is retained in the resulting array.

By using array_values() at the end, we reset the array indexes to consecutive numbers, while maintaining the deduplicated data.

Note:

1. The solution presented prioritizes the last occurrence of the email address. If you prefer to prioritize the first occurrence, reverse the order of the array before iterating through it using array_reverse().
2. The indexes in the resulting array may be rearranged. This is not a major concern if you do not rely on specific indexes.

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