php - Get the minimum and maximum values in an array column

Question

I have an array in this format:

$array = [
    ['id' => 117, 'name' => 'Networking', 'count' => 16],
    ['id' => 188, 'name' => 'FTP', 'count' => 23],
    ['id' => 189, 'name' => 'Internet', 'count' => 48],
];

Is there a good way to retrieve the minimum and maximum values of the 'count' column (16 and 48 respectively)?

I could do this using a few loops, but I wonder if there may be a better way.

Answer 1

In contrast to what others have posted, you cannot use the min()/max() functions for this problem as these functions do not understand the datastructure (array) which are passed in. These functions only work for scalar array elements.

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BEGIN EDIT

The reason why the use of min() and max() seem to yield the correct answer is related to type-casting arrays to integers which is an undefined behaviour:

The behaviour of converting to integer is undefined for other types. Do not rely on any observed behaviour, as it can change without notice.

My statement above about the type-casting was wrong. Actually min() and max() do work with arrays but not in the way the OP needs them to work. When using min() and max() with multiple arrays or an array of arrays elements are compared element by element from left to right:

$val = min(array(2, 4, 8), array(2, 5, 1)); // array(2, 4, 8)
/*
 * first element compared to first element: 2 == 2
 * second element compared to second element: 4 < 5
 * first array is considered the min and is returned
 */

Translated into the OP's problem this shows the reason why the direct use of min() and max() seems to yield the correct result. The arrays' first elements are the id-values, therefore min() and max() will compare them first, incidentally resulting in the correct result because the lowest id is the one with the lowest count and the highest id is the one with the highest count.

END EDIT

---

The correct way would be to use a loop.

$a = array(
        array('id' => 117, 'name' => 'Networking', 'count' => 16),
        array('id' => 188, 'name' => 'FTP', 'count' => 23),
        array('id' => 189, 'name' => 'Internet', 'count' => 48)
);
$min = PHP_INT_MAX;
$max = 0;
foreach ($a as $i) {
    $min = min($min, $i['count']);
    $max = max($max, $i['count']);
}