Bubble Sort

 1 <?php

 2 function swap(&$a, &$b){

 3     $c = $a;

 4     $a = $b;

 5     $b = $c;

 6 }

 7 

 8 # bubble sort

 9 # ascend

10 function sortBubble(&$a){ # a is an array of numbers

11 

12     # length of a

13     $m = count($a);

14 

15     if($m < 2){

16         return;

17     }

18 

19     # swap teller

20     $n = 0;

21 

22     # for m numbers, we have m-1 maxes to bubble to the right

23     for($i=1; $i<=$m-1; $i++){

24 

25         # i=1, a max in m numbers to find;               0, m-1

26         # 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-i

28         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 sort

36             break; # return

37         }

38         else{

39             $n = 0; # reset teller, continue

40         }

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, 5

51 ?>