Sort multidimensional array by multiple columns

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 I need.

I need to sort by the state, then event_type, then date_start.

My array looks like this:

[
    ['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']
]

My desired result is:

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

Solution 1

You need array_multisort

$mylist = array(
    array('ID' => 1, 'title' => 'Boring Meeting', 'event_type' => 'meeting'),
    array('ID' => 2, 'title' => 'Find My Stapler', 'event_type' => 'meeting'),
    array('ID' => 3, 'title' => 'Mario Party', 'event_type' => 'party'),
    array('ID' => 4, 'title' => 'Duct Tape Party', 'event_type' => 'party')
);

# get a list of sort columns and their data to pass to array_multisort
$sort = array();
foreach($mylist as $k=>$v) {
    $sort['title'][$k] = $v['title'];
    $sort['event_type'][$k] = $v['event_type'];
}
# sort by event_type desc and then title asc
array_multisort($sort['event_type'], SORT_DESC, $sort['title'], SORT_ASC,$mylist);

As of PHP 5.5.0:

array_multisort(array_column($mylist, 'event_type'), SORT_DESC,
                array_column($mylist, 'title'),      SORT_ASC,
                $mylist);

$mylist is now:

array (
  0 => 
  array (
    'ID' => 4,
    'title' => 'Duct Tape Party',
    'event_type' => 'party',
  ),
  1 => 
  array (
    'ID' => 3,
    'title' => 'Mario Party',
    'event_type' => 'party',
  ),
  2 => 
  array (
    'ID' => 1,
    'title' => 'Boring Meeting',
    'event_type' => 'meeting',
  ),
  3 => 
  array (
    'ID' => 2,
    'title' => 'Find My Stapler',
    'event_type' => 'meeting',
  ),
)

Solution 2

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!

When the $a value is on the left of the spaceship operator and the $b value is on the right, ASCending sorting is used.

When the $b value is on the left of the spaceship operator and the $a value is on the right, DESCending sorting is used.

When the spaceship operator compares two numeric strings, it compares them as numbers -- so you get natural sorting automagically.

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

Code: (Demo) -- sorts by state ASC, then event_type ASC, then date_start ASC

$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']]
);

The equivalent technique with array_multisort() and a call of array_column() for every sorting criteria is: (Demo)

array_multisort(
    array_column($array, 'state'),
    array_column($array, 'event_type'),
    array_column($array, 'date_start'),
    $array
);

Solution 3

You can do it with usort. The $cmp_function argument could be:

function my_sorter($a, $b) {
    $c = strcmp($a['state'], $b['state']);
    if($c != 0) {
        return $c;
    }

    $c = strcmp($a['event_type'], $b['event_type']);
    if($c != 0) {
        return $c;
    }

    return strcmp($a['date_start'], $b['date_start']);
}

For an arbitrary number of fields in PHP 5.3, you can use closures to create a comparison function:

function make_cmp($fields, $fieldcmp='strcmp') {
    return function ($a, $b) use (&$fields) {
        foreach ($fields as $field) {
            $diff = $fieldcmp($a[$field], $b[$field]);
            if($diff != 0) {
                return $diff;
            }
        }
        return 0;
    }
}

usort($arr, make_cmp(array('state', 'event_type', 'date_start')))

For an arbitrary number of fields of different types in PHP 5.3:

function make_cmp($fields, $dfltcmp='strcmp') {
    # assign array in case $fields has no elements
    $fieldcmps = array();
    # assign a comparison function to fields that aren't given one
    foreach ($fields as $field => $cmp) {
        if (is_int($field) && ! is_callable($cmp)) {
            $field = $cmp;
            $cmp = $dfltcmp;
        }
        $fieldcmps[$field] = $cmp;
    }
    return function ($a, $b) use (&$fieldcmps) {
        foreach ($fieldcmps as $field => $cmp) {
            $diff = call_user_func($cmp, $a[$field], $b[$field]);
            if($diff != 0) {
                return $diff;
            }
        }
        return 0;
    }
}

function numcmp($a, $b) {
    return $a - $b;
}
function datecmp($a, $b) {
    return strtotime($a) - strtotime($b);
}
/**
 * Higher priority come first; a priority of 2 comes before 1.
 */
function make_evt_prio_cmp($priorities, $default_priority) {
    return function($a, $b) use (&$priorities) {
        if (isset($priorities[$a])) {
            $prio_a = $priorities[$a];
        } else {
            $prio_a = $default_priority;
        }
        if (isset($priorities[$b])) {
            $prio_b = $priorities[$b];
        } else {
            $prio_b = $default_priority;
        }
        return $prio_b - $prio_a;
    };
}

$event_priority_cmp = make_evt_prio_cmp(
    array('meeting' => 5, 'party' => 10, 'concert' => 7), 
    0);

usort($arr, make_cmp(array('state', 'event' => $event_priority_cmp, 'date_start' => 'datecmp', 'id' => 'numcmp')))

Solution 4

I have tried to below code and i successfully

array code

$songs =  array(
        '1' => array('artist'=>'Smashing Pumpkins', 'songname'=>'Soma'),
        '2' => array('artist'=>'The Decemberists', 'songname'=>'The Island'),
        '3' => array('artist'=>'Fleetwood Mac', 'songname' =>'Second-hand News')
);

call array sorting function

$songs = subval_sort($songs,'artist'); 
print_r($songs);

array sorting funcation

function subval_sort($a,$subkey) {
    foreach($a as $k=>$v) {
        $b[$k] = strtolower($v[$subkey]);
    }
    asort($b);
    foreach($b as $key=>$val) {
        $c[] = $a[$key];
    }
    return $c;
}

if array reverse sorting function

function subval_sort($a,$subkey) {
        foreach($a as $k=>$v) {
            $b[$k] = strtolower($v[$subkey]);
        }
        arsort($b);
        foreach($b as $key=>$val) {
            $c[] = $a[$key];
        }
        return $c;
    }

Solution 5

Improving on @Stijn Leenknegt's genius code, here is my 2 cent pragmatic function:

$data[] = array('volume' => 67, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 1);
$data[] = array('volume' => 85, 'edition' => 6);
$data[] = array('volume' => 98, 'edition' => 2);
$data[] = array('volume' => 86, 'edition' => 6);
$data[] = array('volume' => 67, 'edition' => 7);

function make_cmp(array $sortValues)
{
    return function ($a, $b) use (&$sortValues) {
        foreach ($sortValues as $column => $sortDir) {
            $diff = strcmp($a[$column], $b[$column]);
            if ($diff !== 0) {
                if ('asc' === $sortDir) {
                    return $diff;
                }
                return $diff * -1;
            }
        }
        return 0;
    };
}

usort($data, make_cmp(['volume' => "desc", 'edition' => "asc"]));

View more solutions

Comments

[Gromski]

You could simplify the nesting quite a bit, and I think you'll need to do something more with the date, but the approach seems best so far.

[outis]

The nice thing about the '%Y-%m-%d' format used in the sample array is string comparison works for date comparison.

[frazras]

@Rob I am very curious how you would sort date_start

[userlond]

For PHP < 5.5 there is polyfill for array_column function github.com/ramsey/array_column. So it's possible to use more elegant way from second code snippet on legacy versions.

[mickmackusa]

This sorts by just column (in an inelegant way), but the OP's question requires the sorting criteria to involve three column values. At best, this is the correct answer to a different question.

[mickmackusa]

This answer is missing its educational explanation. How does this answer solve the OP's question regarding sorting a multidimensional array on three columns?

[mickmackusa]

if ($diff) { return $diff * ($sortDir === 'asc' ? 1 : -1); }

[Scott C Wilson]

This should be the correct answer now that we're all using PHP 7.