Quickest way to find the max frequency element in PHP

Question

I have an array of ids like 127415157,31323794... (range not known). What is the quickest way to find the max frequency ID in PHP?

$array_ids = array()

Answer 1

Try max

$max = max($array_ids);

Answer 2

// Gives us an associative array of id=>count mappings,
$counts = array_count_values($array_ids);
// and sorts it from largest to smallest count
arsort($counts);

// Gets the first key after sorting, which is the id with the largest count
$max_freq_id = key($counts);

stereofrog's suggestion of using array_search() combined with max() may be faster than this, however, since it doesn't need to completely sort the array, and thus will run in O(n) time instead of O(n log n).

Answer 3

$a = array(1, 2, 3, 4, 3, 3, 4, 4, 1, 3);
$r = array_count_values($a);
$k = array_search(max($r), $r);
echo "most frequent value is $k";

Answer 4

Addressing the issue of multiple elements with same frequency:

$values = array(1, 1, 3, 3, 3, 3, 4, 5, 5, 5, 5, 6); 
$freq   = array_count_values($values);
arsort($freq);
$max = $val = key($freq); 
while(next($freq) && current($freq) == $freq[$max]){
    $val .= ','.key($freq);
}

echo " most frequent value is/are $val ";

this will ouput

most frequent value is/are 5,3

also, it's a little faster than using array_search and max combo...