echo "Hello!" ;
    
    // self-defined variales
    $first_name = "Keeru";  #Define a variable
    echo $first_name;
    echo "<br>";
    
    //pre-defined variables
   // echo $_SERVER['SCRIPT_FILENAME'];
    //echo $_SERVER['HTTP_USER_AGENT'];
    $file = $_SERVER['SCRIPT_FILENAME'];
    $user = $_SERVER['HTTP_USER_AGENT'];
    echo $file;
    echo $user, "<br>";
    
    $x = 1; #define a number variable
    $y = 100;
    
    //addition
    $sum = $x +$y ;
    echo $sum, "<br>";
    
    //division
    $result = $x / $y ;
    echo $result , "<br>";
 
    
    //post-increment
    $i = 0;
    //$i = $i + 1;
    echo $i++; // increment i by 1 .After executing this
    //$i
    
    //pre-increment
    $i = 0;
    echo ++$i ,"<br>";
    //new value is immediately returned to //current variable
    
    
   // $name="jane"
    define('GREETING', "WELCOME TO MY WEBSITE"); //define a constant
    echo GREETING ; 
    echo "<br>";
    echo "Hello". GREETING;
    echo "<br>";
    
    define('PI' , 3.14);
    echo  PI;
    echo "The value of PI is" . PI;
     echo "<br>";
     
     // $name=Jane
    define('WELCOME',"WELCOME TO <b>Jane</b>'s WEBSITE");
    echo WELCOME;
    echo "<br>";