PHP sort an array by key by another array(table)

Question

I have an array as table:

$sortLikeThis = [
    '5',
    '3',
    '7'
    '1',
];

$unsorted = [
    [
        'sort' => '7',
        'name' => 'Test',
    ],
    [
        'sort' => '1',
        'name' => 'Test 2',
    ],
    [
        'sort' => '3',
        'name' => 'Test 3',
    ],
    [
        'sort' => '5',
        'name' => 'Test 4',
    ],
    [
        'sort' => '7',
        'name' => 'Test 4',
    ],
]

I want to get sortered array ($unsorted) by sort key like in $sortLikeThis.

e.g.:

$output = [
    [
        'sort' => '5',
        'name' => 'Test 4',
    ],
    [
        'sort' => '3',
        'name' => 'Test 3',
    ],
    [
        'sort' => '7',
        'name' => 'Test',
    ],
    [
        'sort' => '7',
        'name' => 'Test 4',
    ],
    [
        'sort' => '1',
        'name' => 'Test 2',
    ],
]

What should I use?

Related, but not duplicate since this is a multidimensional array: stackoverflow.com/questions/348410/… — nickb
– nickb, Commented Jul 29, 2014 at 14:15

Alma Do · Accepted Answer · 2014-07-29 14:23:01Z

5

Just use usort():

usort($unsorted, function($x, $y) use ($sortLikeThis)
{
   return array_search($x['sort'], $sortLikeThis) - array_search($y['sort'], $sortLikeThis);
});

Check the fiddle.

Hint: with current structure, you'll trigger array_search() (linear time) for each element, which may be slow. Thus, it can be optimized:

$sortLikeThis = array_flip($sortLikeThis);

usort($unsorted, function($x, $y) use ($sortLikeThis)
{
   return $sortLikeThis[$x['sort']] - $sortLikeThis[$y['sort']];
});

With this each lookup will be O(1) since it's a hash-table search.

edited Jul 29, 2014 at 14:23

answered Jul 29, 2014 at 14:16

Alma Do

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