array_count_values

The array_count_values() function in PHP counts the number of instances of each value in an array. array_count_values() returns an associative array using the values of the input array as keys and their frequency in the input as values.

PHP

$a = array('a', 'b','a', 'c', 'c');
$results = array_count_values($a);
print_r($results);
/*
Array (
	[a] => 2
	[b] => 1
	[c] => 2
)
*/

To replicate this functionality in Ruby, we need to use a Hash object, since arrays in Ruby don’t use associative key/value pairs.

Ruby

a = [ "a", "b", "a", "c", "c" ];
result = list.inject({}) do |hash, key|
  hash.include?(key) ? hash[key] += 1 : hash[key] = 1;
  hash
end
 
p result;
# => ["a" => 2, "b" => 1, "c" => 2]