php冒泡排序

 1 $a = [
 2     3,
 3     4,
 4     2,
 5     8,
 6     1,
 7     9
 8 ];
 9 
10 $count = count($a)-1;
11 
12 for($count;$count>1;$count--){
13     for($i=0;$i<=$count;$i++){
14         if($a[$i]>$a[$i+1] && isset($a[$i+1])){
15             //change position
16             $j = $a[$i];
17             $a[$i] = $a[$i+1];
18             $a[$i+1] = $j;
19         }
20     }
21 }