function swap(&$list,$i,$j){

$temp = $list[$i];

$list[$i] = $list[$j];

$list[$j] = $temp;

}

function cocktailSort($list,$n){

$min = 0;

$max = $n-1;

while($min < $max){

for($i = $min;$i < $max;$i++){

if($list[$i] > $list[$i+1]){

swap($list,$i,$i+1);

}

}

$max--;

for($i = $max;$i > $min;$i--){

if($list[$i-1] > $list[$i]){

swap($list,$i-1,$i);

}

}

$min++;

}

return $list;

}

function main(){

$list = array(20,3,5,78,4,1);

$n = count($list);

$list = cocktailSort($list,$n);

var_dump($list);

}

main();