What is the issue with executing PHP code when pressing F5 to refresh the page?

When pressing F5 to refresh the page, the issue with executing PHP code is that it will re-run any database queries or other actions that modify data, potentially causing duplicate entries or undesired changes. To solve this issue, you can use a POST-Redirect-GET pattern where form submissions are handled using POST requests, and after processing the data, you redirect to a new URL using a GET request. 

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    // Process form data and perform necessary actions
    
    // Redirect to a new URL to prevent re-execution of PHP code on page refresh
    header("Location: /success.php");
    exit;
}

Keywords

PHP code execution page refresh session variables caching

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