How Can I Deduplicate a Multi-Dimensional Array in PHP Based on a Specific Key?

PHP Multi-Dimensional Array De-Duplication

In PHP, it is possible to remove duplicates from a multi-dimensional array based on the values of a specific key. Consider the following example:

$array = [
    [
        'name' => 'dave',
        'lastname' => 'jones',
        'email' => 'dave.jones@example.com',
    ],
    [
        'name' => 'john',
        'lastname' => 'jones',
        'email' => 'john.jones@example.com',
    ],
    [
        'name' => 'bruce',
        'lastname' => 'finkle',
        'email' => 'bruce.finkle@example.com',
    ],
];

To remove duplicate sub-arrays based on the email key, one can utilize the following approach:

$uniqueArray = array();
foreach ($array as $key => $subarray) {
    if (!isset($uniqueArray[$subarray['email']])) {
        $uniqueArray[$subarray['email']] = $subarray;
    }
}

This method uses the unique indexes of array keys to create a new array ($uniqueArray) with non-duplicate sub-arrays. The resulting array will only contain the following elements:

[
    'dave.jones@example.com' => [
        'name' => 'dave',
        'lastname' => 'jones',
        'email' => 'dave.jones@example.com',
    ],
    'bruce.finkle@example.com' => [
        'name' => 'bruce',
        'lastname' => 'finkle',
        'email' => 'bruce.finkle@example.com',
    ],
]

Note that the order of the keys in the resulting array is arbitrary. If a specific ordering is desired, additional steps may be necessary. This method can be effectively used to de-duplicate multi-dimensional arrays based on arbitrary criteria.

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