PHP scripts must have the extension .php

They need to be placed in htdocs

They read data as follows; this sequence of steps:

  use CGI; 

  $q = new CGI; 

  $something = $q->param("something"); 

is automatically accomplished by PHP each time. 

Let's develop this: 

http://silo.cs.indiana.edu:46016/0218/two.php

Here's how we do it: 

State in the program will consist of two variables

  a) $balance

  b) $times

Which one of these two should we check to see if we have state? 

Answer: $times 

Here's the program: 

<?
 // state is $balance and $times, which are read automatically

 if ($message && ! $reset) {
   if ($direction == "Up") {
     $balance += 1;
   } else {
     $balance -= 1;
   }
   $times += 1;
 } else { // no state, initialize
   $balance = 0;
   $times = 0;
 }
  
 $message = "You have pushed the button(s) $times times thus far.";

 ?>

<h1> <img src="http://www.cs.indiana.edu/classes/a348/fall2002/smiley.gif"> <? echo $balance ?> </h1>

<? echo $message ?> <p>

<form>

  <input type="submit" name="direction" value="Down">
  <input type="submit" name="direction" value="Up">
  <input type="submit" name="reset" value="Reset">


  <input type="hidden" name="balance"  value="<? echo $balance ?>">
  <input type="hidden" name="times"    value="<? echo $times ?>">
  <input type="hidden" name="message"  value="<? echo $message ?>">


</form>

Note the three buttons, one of which is the Reset button. 

Note the message state variable that is more robust than an integer 
variable (because of 0 checking out as "false" in a boolean context). 

So what does it take to move the state on the server side: 

1. Put a session_start(); at the top of your program. 

2. Replace each hidden field with a session_register call. 

So the program becomes: 

<? session_start(); 

 // state is $balance and $times, which are read automatically

 if ($message && ! $reset) {
   if ($direction == "Up") {
     $balance += 1; 
   } else {
     $balance -= 1;
   } 
   $times += 1; 
 } else { // no state, initialize 

   session_register("message"); 
   session_register("times"); 
   session_register("balance"); 
  
   $balance = 0; 
   $times = 0;
 } 

 $message = "You have pushed the button(s) $times times thus far.";  

 ?> 

<h1> <img src="http://www.cs.indiana.edu/classes/a348/fall2002/smiley.gif"> <? echo $balance ?> </h1> 

<? echo $message ?> <p> 

<form>

  <input type="submit" name="direction" value="Down"> 
  <input type="submit" name="direction" value="Up"> 
  <input type="submit" name="reset" value="Reset"> 

</form> 

We keep an eye on the session folder: 

-bash-3.2$ pwd
/u/dgerman/apache/phpsessions
-bash-3.2$ ls -l
total 0
-bash-3.2$ 

As we start working with the server-side state program we see: 

-bash-3.2$ ls -l
total 8
-rw------- 1 dgerman faculty 85 Feb 19 14:13 sess_c11d385f3434d08b75ca095df95ba94b
-bash-3.2$ cat sess_c11d385f3434d08b75ca095df95ba94b 
message|s:47:"You have pushed the button(s) 2 times thus far.";times|i:2;balance|i:2;-bash-3.2$