Ever stumbled on a tutorial that you feel is of great value but not

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Asked: May 10, 20262026-05-10T23:56:49+00:00 2026-05-10T23:56:49+00:00

Ever stumbled on a tutorial that you feel is of great value but not

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Ever stumbled on a tutorial that you feel is of great value but not quite explained properly? That’s my dilemma. I know THIS TUTORIAL has some value but I just can’t get it.

Where do you call each function?
Which function should be called first and which next, and which third?
Will all functions be called in all files in an application?
Does anyone know of a better way cure the ‘Back Button Blues’?

I’m wondering if this will stir some good conversation that includes the author of the article. The part I’m particularly interested in is controlling the back button in order to prevent form duplicate entries into a database when the back button is pressed. Basically, you want to control the back button by calling the following three functions during the execution of the scripts in your application. In what order exactly to call the functions (see questions above) is not clear from the tutorial.

All forwards movement is performed by using my scriptNext function. This is called within the current script in order to activate the new script.
function scriptNext($script_id) // proceed forwards to a new script {    if (empty($script_id)) {       trigger_error('script id is not defined', E_USER_ERROR);    } // if     // get list of screens used in this session    $page_stack = $_SESSION['page_stack'];    if (in_array($script_id, $page_stack)) {       // remove this item and any following items from the stack array       do {          $last = array_pop($page_stack);       } while ($last != $script_id);    } // if     // add next script to end of array and update session data    $page_stack[] = $script_id;    $_SESSION['page_stack'] = $page_stack;     // now pass control to the designated script    $location = 'http://' .$_SERVER['HTTP_HOST'] .$script_id;    header('Location: ' .$location);     exit;  } // scriptNext 
When any script has finished its processing it terminates by calling my scriptPrevious function. This will drop the current script from the end of the stack array and reactivate the previous script in the array.
function scriptPrevious() // go back to the previous script (as defined in PAGE_STACK) {    // get id of current script    $script_id = $_SERVER['PHP_SELF'];     // get list of screens used in this session    $page_stack = $_SESSION['page_stack'];    if (in_array($script_id, $page_stack)) {       // remove this item and any following items from the stack array       do {          $last = array_pop($page_stack);       } while ($last != $script_id);       // update session data       $_SESSION['page_stack'] = $page_stack;    } // if     if (count($page_stack) > 0) {       $previous = array_pop($page_stack);       // reactivate previous script       $location = 'http://' .$_SERVER['HTTP_HOST'] .$previous;    } else {       // no previous scripts, so terminate session       session_unset();       session_destroy();       // revert to default start page       $location = 'http://' .$_SERVER['HTTP_HOST'] .'/index.php';    } // if     header('Location: ' .$location);     exit;  } // scriptPrevious 
Whenever a script is activated, which can be either through the scriptNext or scriptPrevious functions, or because of the BACK button in the browser, it will call the following function to verify that it is the current script according to the contents of the program stack and take appropriate action if it is not.
function initSession() // initialise session data {    // get program stack    if (isset($_SESSION['page_stack'])) {       // use existing stack       $page_stack = $_SESSION['page_stack'];    } else {       // create new stack which starts with current script       $page_stack[] = $_SERVER['PHP_SELF'];       $_SESSION['page_stack'] = $page_stack;    } // if     // check that this script is at the end of the current stack    $actual = $_SERVER['PHP_SELF'];    $expected = $page_stack[count($page_stack)-1];    if ($expected != $actual) {       if (in_array($actual, $page_stack)) {// script is within current stack, so remove anything which follows       while ($page_stack[count($page_stack)-1] != $actual ) {             $null = array_pop($page_stack);          } // while          $_SESSION['page_stack'] = $page_stack;       } // if       // set script id to last entry in program stack       $actual = $page_stack[count($page_stack)-1];       $location = 'http://' .$_SERVER['HTTP_HOST'] .$actual;       header('Location: ' .$location);       exit;    } // if     ... // continue processing  } // initSession 
The action taken depends on whether the current script exists within the program stack or not. There are three possibilities:

The current script is not in the $page_stack array, in which case it is not allowed to continue. Instead it is replaced by the script which is at the end of the array.

The current script is in the $page_stack array, but it is not the last entry. In this case all following entries in the array are removed.

The current script is the last entry in the $page_stack array. This is the expected situation. Drinks all round!