Sort array based on count of any value - php

Question

I have an array which looks like
Array
(
[0] => Array
(
[id] => 39662
[points] => 24
[subject] => 112
)
[1] => Array
(
[id] => 39609
[points] => 24
[subject] => 87
)
[2] => Array
(
[id] => 39610
[points] => 23
[subject] => 77
)
[3] => Array
(
[id] => 39608
[points] => 23
[subject] => 87
)
[4] => Array
(
[id] => 39606
[points] => 22
[subject] => 60
)
[5] => Array
(
[id] => 39604
[points] => 19
[subject] => 75
)
[6] => Array
(
[id] => 39595
[points] => 18
[subject] => 60
)
[7] => Array
(
[id] => 39605
[points] => 18
[subject] => 47
)
[8] => Array
(
[id] => 39650
[points] => 17
[subject] => 87
)
[9] => Array
(
[id] => 39660
[points] => 17
[subject] => 55
)
)
Now I want to sort then based on count of key subject. You can see that subjuet = 87 have 3 records and subject = 60 has two records, so all three records of 87 should display first , after this records of 60 , then others.
I tried array_multisort but its not giving expected result.
Thanks

Answer 1

As per your desired output, you just need to array_map() with array_multisort(),
Example:
<?php
// Test Array
$array = array(
array('id'=>39662,'points'=>'24','subject'=>112),
array('id'=>39609,'points'=>'24','subject'=>87),
array('id'=>39610,'points'=>'23','subject'=>77),
array('id'=>39608,'points'=>'23','subject'=>87),
array('id'=>39606,'points'=>'22','subject'=>60),
array('id'=>39604,'points'=>'19','subject'=>75),
array('id'=>39595,'points'=>'18','subject'=>60),
array('id'=>39605,'points'=>'18','subject'=>47),
array('id'=>39650,'points'=>'17','subject'=>87),
array('id'=>39660,'points'=>'17','subject'=>55),
);
$newArr = array(); // initialize the new Array
foreach ($array as $key => $value)
{
$newArr[$value['subject']][] = $value;
}
array_multisort(array_map('count', $newArr), SORT_DESC, $newArr); // using array_multisort() and Sort as DESC order by using array_map()
echo "<pre>";
print_r($newArr);
?>
Result:
Array
(
[0] => Array
(
[0] => Array
(
[id] => 39609
[points] => 24
[subject] => 87
)
[1] => Array
(
[id] => 39608
[points] => 23
[subject] => 87
)
[2] => Array
(
[id] => 39650
[points] => 17
[subject] => 87
)
)
[1] => Array
(
[0] => Array
(
[id] => 39606
[points] => 22
[subject] => 60
)
[1] => Array
(
[id] => 39595
[points] => 18
[subject] => 60
)
)
[2] => Array
(
[0] => Array
(
[id] => 39604
[points] => 19
[subject] => 75
)
)
[3] => Array
(
[0] => Array
(
[id] => 39605
[points] => 18
[subject] => 47
)
)
[4] => Array
(
[0] => Array
(
[id] => 39610
[points] => 23
[subject] => 77
)
)
[5] => Array
(
[0] => Array
(
[id] => 39660
[points] => 17
[subject] => 55
)
)
[6] => Array
(
[0] => Array
(
[id] => 39662
[points] => 24
[subject] => 112
)
)
)

Answer 2

Try the following method for your case
$data[] = array('points' => 67, 'subject' => 2);
$data[] = array('points' => 86, 'subject' => 1);
$data[] = array('points' => 85, 'subject' => 6);
$data[] = array('points' => 98, 'subject' => 2);
$data[] = array('points' => 86, 'subject' => 6);
$data[] = array('points' => 67, 'subject' => 7);
// Obtain a list of columns
foreach ($data as $key => $row) {
$subject[$key] = $row['subject'];
}
// Sort the data with volume descending, edition ascending
// Add $data as the last parameter, to sort by the common key
array_multisort($subject, SORT_DESC, $data);
Example usage with my array from the php manual.
Output of the above was
Array
(
[0] => Array
(
[points] => 67
[subject] => 7
)
[1] => Array
(
[points] => 85
[subject] => 6
)
[2] => Array
(
[points] => 86
[subject] => 6
)
[3] => Array
(
[points] => 67
[subject] => 2
)
[4] => Array
(
[points] => 98
[subject] => 2
)
[5] => Array
(
[points] => 86
[subject] => 1
)
)

Answer 3

function array_sort($array, $key){
$new_array = array();
$sortable_array = array();
if (count($array) > 0) {
foreach ($array as $k => $v) {
if (is_array($v)) {
foreach ($v as $k2 => $v2) {
if ($k2 == $key) {
$sortable_array[$k] = $v2;
}
}
} else {
$sortable_array[$k] = $v;
}
}
asort($sortable_array);
}
foreach ($sortable_array as $k => $v) {
$new_array[$k] = $array[$k];
}
}
return $new_array;
}
array_sort($a, 'subjects');
//$a is array which want to sort