How Can I Efficiently Flatten a Multidimensional Numeric-Keyed Array in PHP?

Simplifying Multidimensional Arrays into Linear Structures

Converting multidimensional arrays into their one-dimensional counterparts can often be a daunting task, especially when dealing with arrays containing solely numeric keys. However, there is a simple yet elegant solution to flatten these structures, utilizing PHP's array functions.

Answer Explained

The solution employs the array_reduce() function in conjunction with array_merge(). array_reduce() iterates through each element of the array, applying a user-defined function to accumulate a final reduced value. In this case, we pass in the array_merge() function, which combines two arrays into a single array.

By specifying an empty array as the initial value of the reduce operation, we ensure that the final result is an array containing all the elements from the multidimensional array. Each iteration concatenates the current subarray with the accumulator, effectively flattening the input.

Example Implementation

Consider the multidimensional array provided in the question:

$array = [
    [0 => 'foo', 1 => 'bar', 2 => 'hello'],
    [0 => 'world', 1 => 'love'],
    [0 => 'stack', 1 => 'overflow', 2 => 'yep', 3 => 'man'],
];

To flatten this array, we can simply use the following code:

$result = array_reduce($array, 'array_merge', []);

This would produce the desired one-dimensional array:

$result = [
    'foo', 'bar', 'hello', 'world', 'love', 'stack', 'overflow', 'yep', 'man'
];

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