What common mistake in PHP scripts can prevent data from being transmitted using the post method?

One common mistake in PHP scripts that can prevent data from being transmitted using the post method is not setting the correct form action attribute. If the form action attribute is not set or set to a different URL, the data will be sent using the default get method instead of the post method. To solve this issue, make sure the form action attribute is set to the correct URL where the data should be submitted.

<form method="post" action="process_form.php">
    <!-- form fields here -->
    <input type="submit" value="Submit">
</form>