Counting distinct values in multidimensional array - php

Question

I'm having real problems trying to figure this one out.
I have a PHP array which looks like this:
$info = array();
$info[0] = array(
'car' => 'Audi',
'previous_car' => 'BMW'
);
$info[1] = array(
'car' => 'Audi',
'previous_car' => 'Seat'
);
$info[2] = array(
'car' => 'Audi',
'previous_carg' => 'BMW'
);
$info[3] = array(
'car' => 'BMW',
'previous_car' => 'BMW'
);
$info[4] = array(
'car' => 'Ford',
'previous_car' => 'Seat'
);
I need to do some sorting on this, so the result looks like this:
Array (
car [
'Audi' => 3,
'BMW' => 1,
'Ford' => 1
],
previous_car [
'BMW' => 3,
'Seat' => 2
]
);
I need to count distinct occurrences of a value in the same key, but the search is made upon couple of arrays. I was trying to use array_value_count(), but I doesn't work well on multidimensional arrays.
I am trying to avoid the looping, since it can be overkill if the array is large.
I will be very grateful for all the help.

Answer 1

If you're running PHP 5.5, you can use:
$newArray = array(
'car' => array_count_values(array_column($info, 'car')),
'previous_car' => array_count_values(array_column($info, 'previous_car'))
);
var_dump($newArray);
For versions of PHP prior to 5.5
$newArray = array(
'car' => array_count_values(
array_map(
function($value) {
return $value['car'];
},
$info
)
),
'previous_car' => array_count_values(
array_map(
function($value) {
return $value['previous_car'];
},
$info
)
)
);
var_dump($newArray);

Answer 2

In a more object orientated way you can solve it as follows
$values = new ArrayObject();
$iterator = new RecursiveArrayIterator($info);
iterator_apply($iterator, 'countDistinct', array($iterator, $values));
function countDistinct($iterator, $values) {
while ( $iterator -> valid() ) {
if ( $iterator -> hasChildren() ) {
countDistinct($iterator -> getChildren(), $values);
} else {
if (!$values->offsetExists($iterator->key())) {
$values->offsetSet($iterator->key(), new ArrayObject());
}
if (!$values->offsetGet($iterator->key())->offsetExists($iterator->current())) {
$values->offsetGet($iterator->key())
->offsetSet($iterator->current(), 1);
} else {
$values->offsetGet($iterator->key())
->offsetSet($iterator->current(),
$values->offsetGet($iterator->key())->offsetGet($iterator->current()) + 1);
}
}
$iterator -> next();
}
}
Sure, with this example you do not avoid the loop. But with the ArrayObject and the RecursiveArrayIterator you will have some memory and performance advantages.
The result of this will exactly match your expected result, which you can easyliy iterate with the getIterator() function of the ArrayObject.

Answer 3

You can write a function that will sort your data but for now check this out:
http://www.php.net/manual/en/function.array-multisort.php

Answer 4

Here is what might help you:
$returnArray = array('car' => NULL, 'previous_car' => NULL);
foreach($info as $newInfo) {
$returnArray['car'][] = $newInfo['car'];
$returnArray['previous_car'][] = $newInfo['previous_car'];
}
$ret['car'] = array_count_values($returnArray['car']);
$ret['previous_car'] = array_count_values($returnArray['previous_car']);
var_dump($ret);
This returns:
array (size=2)
'car' =>
array (size=3)
'Audi' => int 3
'BMW' => int 1
'Ford' => int 1
'previous_car' =>
array (size=2)
'BMW' => int 3
'Seat' => int 2