Remove duplicate values from array: array_unique() variations and alternatives

One of my favorite features of PHP is the tremendous wealth of built-in functions that perform all kinds of useful tasks. Practically any basic operation I ever need to do can be done with a simple PHP function call. This was the case when I needed to remove duplicate values from an array of strings. array_unique() to the rescue.

However, it turns out that for simple dupe removal operations, there are alternatives to array_unique() that perform noticeably faster.

To replace array_unique(), try this faster alternative:

array_flip(array_flip($array))

Note that both functions above leave “gaps” in the resulting array; if $array[2] is a dupe and removed, $array[3] does NOT become $array[2]. If you’d like to reindex/reorder the resulting array, try

array_values(array_unique($array))

And here’s a faster alternative: (source)

array_keys(array_flip($array))

If you’d like to remove case insensitive duplicates, try the following function: (source)

function array_iunique($array) {
    return array_intersect_key($array,array_unique(
                 array_map(strtolower,$array)));
}

Or this faster alternative:

function array_iunique($array) {
	return array_intersect_key($array,
                 array_flip(array_flip(array_map(strtolower,$array))));
}

Sorry for the really infrequent updates. 3-4 hour commutes per day and long work hours is killing my free time.

Merry Christmas to all!

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