<?php
foreach ($ary=array("○", "○", "○", "△", "△", "☓") as $val1)
	foreach ($ary as $val2)
		$a[$x=$val1>$val2?$val1.$val2:$val2.$val1] = isset($a[$x]) ? ++$a[$x] : 1;
arsort($a);
print_r($a);