Sort multidimensional array by multiple keys

Question

I\'m trying to sort a multidimensional array by multiple keys, and I have no idea where to start. I looked at uasort, but wasn\'t quite sure how to write a function for what

Answer 1

PHP7 Makes sorting by multiple columns SUPER easy with the spaceship operator (<=>) aka the "Combined Comparison Operator" or "Three-way Comparison Operator".

Resource: https://wiki.php.net/rfc/combined-comparison-operator

Sorting by multiple columns is as simple as writing balanced/relational arrays on both sides of the operator. Easy done!

I have not used uasort() because I don't see any need to preserve the original indexes.

Code: (Demo)

$array = [
    ['ID' => 1, 'title' => 'Boring Meeting', 'date_start' => '2010-07-30', 'event_type' => 'meeting', 'state' => 'new-york'],
    ['ID' => 2, 'title' => 'Find My Stapler', 'date_start' => '2010-07-22', 'event_type' => 'meeting', 'state' => 'new-york'],
    ['ID' => 3, 'title' => 'Mario Party', 'date_start' => '2010-07-22', 'event_type' => 'party', 'state' => 'new-york'],
    ['ID' => 4, 'title' => 'Duct Tape Party', 'date_start' => '2010-07-28', 'event_type' => 'party', 'state' => 'california']
];

usort($array, function($a, $b) {
    return [$a['state'], $a['event_type'], $a['date_start']]
           <=>
           [$b['state'], $b['event_type'], $b['date_start']];
});

var_export($array);

Output

array (
  0 => 
  array (
    'ID' => 4,
    'title' => 'Duct Tape Party',
    'date_start' => '2010-07-28',
    'event_type' => 'party',
    'state' => 'california',
  ),
  1 => 
  array (
    'ID' => 2,
    'title' => 'Find My Stapler',
    'date_start' => '2010-07-22',
    'event_type' => 'meeting',
    'state' => 'new-york',
  ),
  2 => 
  array (
    'ID' => 1,
    'title' => 'Boring Meeting',
    'date_start' => '2010-07-30',
    'event_type' => 'meeting',
    'state' => 'new-york',
  ),
  3 => 
  array (
    'ID' => 3,
    'title' => 'Mario Party',
    'date_start' => '2010-07-22',
    'event_type' => 'party',
    'state' => 'new-york',
  ),
)

p.s. Arrow syntax with PHP7.4 and higher (Demo)...

usort($array, fn($a, $b) => [$a['state'], $a['event_type'], $a['date_start']] <=> [$b['state'], $b['event_type'], $b['date_start']]);