Ordering PHP arrays based on duplicate values

问题:

I have an array which contains duplicate values. I want to sort the array so that the values with the most duplicates appear first in line. Here's an example of my array:

array(1, 2, 3, 2, 1, 2, 2);

I want to sort this array so that it orders itself based on the amount of duplicates into the following:

array(2, 1, 3);

'2' has the most duplicates so it's sorted first, followed by values will less duplicates. Does anyone know how I can accomplish this?

回答1:

 $acv=array_count_values($array); //  1=>2, 2=>3,3=>1
 arsort($acv); //save keys,           2=>3, 1=>2, 3=>1 
 $result=array_keys($acv); //get only keys   2,1,3

回答2:

1. traverse the array, and increment OCCURENCES in another key-value associative array.
2. sort the second array by values.
3. get array_keys of second array.