Button click counter [PHP]

Question

I tried to create a variable to store a count of button clicked. Unfortunetlly i get this error:

 Undefined variable: counter

It's my code:

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $counter = isset($_POST['counter']) ? $_POST['counter'] : 0;
    if(isset($_POST["button"])){
        $counter++;
        echo $counter;
    }
}

And it's a form:

<form action = "<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" method = post>
    <input type = "submit" name = "button" value = "Submit" >
    <input type = "hidden" name = "counter" value = "<?php print $counter; ?>"; />
</form>

Anybody know what i'm doing wrong?

Answer 1

Alternatively, if you want to save the counter, you can use sessions. Like this:

session_start();

// if counter is not set, set to zero
if(!isset($_SESSION['counter'])) {
    $_SESSION['counter'] = 0;
}

// if button is pressed, increment counter
if(isset($_POST['button'])) {
    ++$_SESSION['counter'];
}    

// reset counter
if(isset($_POST['reset'])) {
    $_SESSION['counter'] = 0;
}

?>

<form method="POST">
    <input type="hidden" name="counter" value="<?php echo $_SESSION['counter']; ?>" />
    <input type="submit" name="button" value="Counter" />
    <input type="submit" name="reset" value="Reset" />
    <br/><?php echo $_SESSION['counter']; ?>
</form>

By the way, your current code will show an Undefined index error because you are echoing $counter on your form but you haven't initialized it yet. It will only exist, upon first form submission, not upon first normal load of the page.

Answer 2

There is no error in your code. Its working at my end. You need to check two points:

1. PHP code should be above on HTML, HTML code will come after PHP code. So that $counter variable will be initialized.

2. PHP and HTML code should be on same page.

---

As OP edited the question: So, the line $counter = isset($_POST['counter']) ? $_POST['counter'] : 0; should not be in if-block. To be sure, ** Make this line as a first line of PHP file. Then only $counter variable will be available for whole page.