How can developers troubleshoot and debug issues related to form data submission in PHP when $_POST variables are not populated as expected?

If $_POST variables are not populated as expected when submitting form data in PHP, developers can troubleshoot the issue by checking the form's method attribute (it should be set to "post"), ensuring that the form fields have the correct name attributes that match the keys in the $_POST array, and verifying that the form data is being sent correctly. Additionally, developers can use var_dump($_POST) to inspect the contents of the $_POST array for debugging purposes. 

<form method="post" action="process_form.php">
    <input type="text" name="username">
    <input type="password" name="password">
    <button type="submit">Submit</button>
</form>
```

In the PHP file (process_form.php) that processes the form submission:

```php
<?php
// Check if form data is being submitted via POST method
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Check if the expected form fields are populated in the $_POST array
    if (isset($_POST['username']) && isset($_POST['password'])) {
        // Process the form data
        $username = $_POST['username'];
        $password = $_POST['password'];
        
        // Debugging: Inspect the contents of the $_POST array
        var_dump($_POST);
    } else {
        echo "Form fields are not populated as expected.";
    }
}
?>

Keywords

$_POST form data troubleshooting debugging variables

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