Understanding Form Submission and Delete Functionality in PHP
As a developer, it’s essential to grasp how form submission works, especially when dealing with multiple forms on a page. In this article, we’ll delve into the world of form submission, focus on understanding which variables are passed during form submission, and explore solutions for deleting rows from a table using a submit button.
Table of Contents
Understanding Form Submission
When a form is submitted, the server receives a request with several key pieces of information. The most crucial aspect is understanding which variables are passed during this process.
Variables Passed During Form Submission
Form Name
The form name refers to the unique identifier assigned to the form element in HTML code. In our case, all buttons have the same name attribute set to “verwijder”.
<form method="post">
<input type="submit" class="dropdown-item text-danger" name="verwijder" value="Verwijder"/>
</form>
This means that when you submit a form with this name, only one button will be executed.
Hidden Input Fields
Hidden input fields are used to store values that should not be visible on the webpage. In our case, we can use hidden input fields to store the reservation ID:
<input type="hidden" name="resid" value="<?= $resid ?>" />
By including this field in our form, we can ensure that only one button will be executed when multiple buttons are clicked.
Button Names and Values
Button names and values refer to the name attribute and the value of each button. Since all buttons have the same name (verwijder), they will all trigger the delete code when submitted:
<form method="post">
<input type="submit" class="dropdown-item text-danger" name="verwijder" value="Verwijder"/>
</form>
However, we can avoid this issue by using a hidden input field to store the reservation ID.
The Issue with Multiple Submit Buttons
When you have multiple submit buttons on a page and they all have the same name attribute, they will all be executed when submitted. This is because PHP treats the $_POST['verwijder'] superglobal array as an associative array where each key corresponds to the value of the name attribute in each form element.
In our example, this means that when you click on multiple buttons, all of them will trigger the delete code and delete both rows from the database:
if(isset($_POST['verwijder']))
{
$resid = $pers->reserveringnummer;
// Delete code here
}
This is not the desired behavior.
Solution: Using a Hidden Input Field to Store the Reservation ID
To solve this issue, we need to modify our form to include a hidden input field that stores the reservation ID. Here’s how you can do it:
<form method="post">
<input type="hidden" name="resid" value="<?= $resid ?>" />
<input type="submit" class="dropdown-item text-danger" name="verwijder" value="Verwijder"/>
</form>
By including this hidden input field in our form, we ensure that only one button will be executed when multiple buttons are clicked. The value of the hidden input field is set to the reservation ID using a PHP echo statement:
foreach ($result as $pers) {
// some row data
?>
<form method="post">
<input type="hidden" name="resid" value="<?php echo $resid; ?>" />
<input type="submit" class="dropdown-item text-danger" name="verwijder" value="Verwijder"/>
</form>
<?php
}
With this solution, you can delete rows from the database by clicking on any of the submit buttons. The hidden input field ensures that only one button will be executed.
Conclusion
In conclusion, understanding how form submission works is essential for developing efficient and effective web applications. By grasping which variables are passed during form submission, we can solve complex issues like deleting rows from a table using multiple submit buttons.
By using a hidden input field to store the reservation ID, we can avoid the issue of multiple buttons triggering the delete code when submitted. This approach ensures that only one button will be executed, making our application more user-friendly and efficient.
Last modified on 2023-08-07