What will be the output of the following PHP code ?

<?php
$a = 97;
switch(?$a)
{
case "a":
    print "hi";
    break;
case 97:
    print "hello";
    break;
default:
    print "hi1";
}
?>

<?php
$x;
if ($x)
    print "hi" ;
else
    print "how are u";
?>

<?php
$x = 0;
if ($x++)
    print "hi";
else
    print "how are u";
?>

<?php
$x;
if ($x == 0)
    print "hi" ;
else
    print "how are u";
    print "hello"
?>

<?php
$x = 0;
if ($x == 1)
    if ($x >= 0)
	print "true";
    else
	print "false"; 
?>