What common mistakes can lead to data being written to a file before form validation is completed in PHP?

One common mistake that can lead to data being written to a file before form validation is completed in PHP is not checking if the form has been submitted before processing the data. To solve this issue, you should always check if the form has been submitted before writing data to a file. 

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Perform form validation here
    // If form validation passes, then write data to file
    // Example: 
    $data = $_POST['data'];
    
    // Write data to file
    $file = fopen("data.txt", "w");
    fwrite($file, $data);
    fclose($file);
}
?>

Keywords

file writing form validation PHP data integrity security vulnerability

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