1 <?php 2 function swap(&$a, &$b){ 3     $c = $a; 4     $a = $b; 5     $b = $c; 6 } 7  8 # bubble sort 9 # ascend10 function sortBubble(&$a){ # a is an array of numbers11 12     # length of a13     $m = count($a);14 15     if($m < 2){16         return;17     }18 19     # swap teller20     $n = 0;21 22     # for m numbers, we have m-1 maxes to bubble to the right23     for($i=1; $i<=$m-1; $i++){24 25         # i=1, a max in m numbers to find;               0, m-126         # i=2, a max in m-1 numbers on the left to find; 0, m-2 27         # i=3, a max in m-2 numbers on the left to find; 0, m-3; m-i28         for($j=0; $j<$m-$i; $j++){29             if($a[$j] > $a[$j+1]){30                 swap($a[$j], $a[$j+1]);31                 $n = 1;32             }33         }34 35         if($n == 0){ # no swap happened, finish the sort36             break; # return37         }38         else{39             $n = 0; # reset teller, continue40         }41     }42 43     return;44 }45 46 $arr = range(5, 0);47 sortBubble($arr);48 echo implode(', ', $arr);49 50 // 0, 1, 2, 3, 4, 551 ?>