<html>
<head>
<title></title>
<meta charset="utf-8">
</head>
<body>
<?php
for($a = 1;$a < 20;$a += 2)
{
echo $a;
echo "<br />";
}
$a = 1;
while($a < 20)
{
echo $a;
echo "<br />";
$a = $a + 2;
}
$a = 1;
do{
echo $a;
echo "<br />";
$a = $a + 2;
}while($a < 20);
?>
</body>
</html>