Using Hidden Fields to Save State

The script in Listing 10.6 has no way of knowing how many guesses a user has made, but we can use a hidden field to keep track of this. A hidden field behaves exactly the same as a text field, except that the user cannot see it unless he views the HTML source of the document that contains it.

Take the original numguess.php script, and save a copy as numguess2.php. In the new version, add a line after the initial assinment of the $num_to_guess variable:

 $num_tries = (isset($_POST[num_tries])) ? $num_tries + 1 : 1; 

This line initializes a variable called $num_TRies, and assigns a value to it. If the form has not yet been submitted ($_POST[num_tries] is empty), the value of the $num_TRies variable is 1 because we will be on our first attempt at guessing the number. If the form has already been sent, then the new value is the value of $_POST[num_tries], plus 1.

The next change comes after the HTML level H1 heading:

 <p><strong>Guess number:</strong> <?php echo $num_tries; ?></p> 

This new line simply prints the current value of $num_tries to the screen.

Finally, before the HTML code for the form submission button, add the hidden field. This field will save the incremented value of $num_TRies:

 <input type="hidden" name="num_tries" value="<?php echo $num_tries; ?>"> 

Listing 10.7 shows the new script, in its entirety.

Listing 10.7. Saving State with a Hidden Field
 1: <?php 2: $num_to_guess = 42; 3: $num_tries = (isset($_POST[num_tries])) ? $_POST[num_tries] + 1 : 1; 4: if (!isset($_POST[guess])) { 5:    $message = "Welcome to the guessing machine!"; 6: } else if ($_POST[guess] > $num_to_guess) { 7:    $message = "$_POST[guess] is too big! Try a smaller number."; 8: } else if ($_POST[guess] < $num_to_guess) { 9:    $message = "$_POST[guess] is too small! Try a larger number."; 10: } else { // must be equivalent 11:    $message = "Well done!"; 12: } 13: $guess = $_POST[guess]; 14: ?> 15: <html> 16: <head> 17: <title> Saving state with a hidden field</title> 18: </head> 19: <body> 20: <h1><?php echo $message ?></h1> 21: <p><strong>Guess number:</strong> <?php echo $num_tries; ?></p> 22: <form action="<?php echo $_SERVER[PHP_SELF]; ?>" method="POST"> 23: <p><strong>Type your guess here:</strong> 24: <input type="text" name="guess" value="<?php echo $guess; ?>"> 25: <input type="hidden" name="num_tries" value="<?php echo $num_tries; ?>"> 26: <p><input type="submit" value="submit your guess"></p> 27: </form> 28: </body> 29: </html> 

Save the numguess2.php file, and place it in your Web server document root. Access the form a few times with your Web browser, and try to guess the number (pretend you don't already know it). The counter should increment by one, with each access.

Sams Teach Yourself PHP MySQL and Apache All in One
Sams Teach Yourself PHP, MySQL and Apache All in One (4th Edition)
ISBN: 067232976X
EAN: 2147483647
Year: 2003
Pages: 333
Authors: Julie Meloni

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