is_null() Function函数详解

bool is_null ( mixed $var )

<?php
	$var1 = TRUE;
	if (is_null($var1))
	{
	  echo 'Variable is  NULL';
	}
	else
	{
	  echo 'Variable is not NULL';
	}
?>

<?php
	$x= 100;
	unset($x);
	echo is_null($x);
?>

<?php  
	$x = NULL; 
	$y = "\0";
	is_null($x) ? print_r("True\n") : print_r("False\n");
	echo "<br/>";
	is_null($y) ? print_r("True\n") : print_r("False\n");
?>