How to Sort a Multidimensional PHP Array by Sub-array Value?

Sorting a Multidimensional Array by Sub-array Value in PHP

In PHP, arrays can be multidimensional, meaning they can contain arrays within arrays. A common use case is to sort such arrays based on a specific key within the nested sub-arrays.

Sorting by a String Key

Consider the following array:

$array = [
    [
        'configuration_id' => 10,
        'id' => 1,
        'optionNumber' => '3',
        'optionActive' => 1,
        'lastUpdated' => '2010-03-17 15:44:12'
    ],
    [
        'configuration_id' => 9,
        'id' => 1,
        'optionNumber' => '2',
        'optionActive' => 1,
        'lastUpdated' => '2010-03-17 15:44:12'
    ],
    [
        'configuration_id' => 8,
        'id' => 1,
        'optionNumber' => '1',
        'optionActive' => 1,
        'lastUpdated' => '2010-03-17 15:44:12'
    ]
];

To sort this array in ascending order based on the 'optionNumber' key, we can use usort along with an anonymous function:

usort($array, function ($a, $b) {
    return strcmp($a['optionNumber'], $b['optionNumber']);
});

This function compares the 'optionNumber' values of each sub-array and returns 1 if the first value is greater, -1 if it's smaller, or 0 if they're equal. This comparison is case-sensitive.

Sorting by an Integer Key

If the 'optionNumber' key contains integers, we can use the following function:

usort($array, function ($a, $b) {
    return $a['optionNumber'] - $b['optionNumber'];
});

This comparison will sort the array in ascending numerical order.

Considerations

• For PHP versions 5.3 and above, use the spaceship operator (<=>) instead of subtraction to prevent overflow/truncation problems.
• Note that these solutions assume the 'optionNumber' key exists in all sub-arrays and is of the expected type.

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