How can I merge multiple PHP arrays while removing duplicate values?

Merging and Deduplicating Arrays in PHP

When working with PHP arrays, it's often necessary to merge multiple arrays into a single array. However, it's crucial to avoid duplicate values in the final array.

Merging Two Arrays

To merge two arrays, you can use the array_merge() function:

$array1 = [
    (object) [
        'ID' => 749,
        'post_author' => 1,
        'post_date' => '2012-11-20 06:26:07',
        'post_date_gmt' => '2012-11-20 06:26:07'
    ]
];

$array2 = [
    (object) [
        'ID' => 749,
        'post_author' => 1,
        'post_date' => '2012-11-20 06:26:07',
        'post_date_gmt' => '2012-11-20 06:26:07'
    ]
];

$mergedArray = array_merge($array1, $array2);

The $mergedArray will contain both elements from $array1 and $array2. However, it will also contain the duplicate object from $array2, which may not be desirable.

Removing Duplicates

To remove duplicates, you can use the array_unique() function. This function takes an array as its argument and returns a new array with duplicate values removed. You can combine array_merge() and array_unique() to both merge arrays and remove duplicates:

$mergedAndUniquedArray = 
array_unique(array_merge($array1, $array2), SORT_REGULAR);

The SORT_REGULAR flag ensures that the array is sorted by the values of its elements before duplicates are removed. This can be important if you want to maintain the order of the original arrays when merging them.

You can also use a combination of array_map() and spl_object_hash() to remove duplicate objects from arrays:

$removeDuplicatesUsingObjects = function ($object) {
    return spl_object_hash($object);
};

$mergedAndUniquedArray = array_map($removeDuplicatesUsingObjects, 
array_merge($array1, $array2));
$mergedAndUniquedArray = array_unique($mergedAndUniquedArray);

This method uses the spl_object_hash() function to generate a unique identifier for each object, and then removes duplicates based on these identifiers.

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