//NULL.php

<?php
    $var1 = "Hello";
    $var2 = NULL;
    $var3 = 10;
    $var4 = 20;
    
    if(is_null($var1))  print("var1 contains NULL\n");
    else print("var1 contains $var1\n");

    if(is_null($var2)) print("var2 contains NULL\n");
    else print("var2 contains $var2\n");

    if(is_null($var3)) print("var3 contains NULL\n");
    else print("var3 contains $var3\n");

    if(is_null($var4)) print("var4 contains NULL\n");
    else print("var4 contains $var4\n");        
    
    //unsetting all variables
    unset($var1);
    unset($var2);
    unset($var3);
    unset($var4);

    if(is_null($var1))  print("var1 contains NULL\n");
    else print("var1 contains $var1\n");

    if(is_null($var2)) print("var2 contains NULL\n");
    else print("var2 contains $var2\n");

    if(is_null($var3)) print("var3 contains NULL\n");
    else print("var3 contains $var3\n");

    if(is_null($var4)) print("var4 contains NULL\n");
    else print("var4 contains $var4\n");            
?>