How can the form be validated to prevent submission with pre-defined values in PHP?

To prevent submission with pre-defined values in PHP, you can validate the form data before processing it. One way to do this is by checking if the submitted values match the pre-defined values and displaying an error message if they do. This can help ensure that only valid data is submitted. 

// Check if form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Define pre-defined values
    $predefined_values = array("value1", "value2", "value3");
    
    // Get form data
    $submitted_value = $_POST["input_field"];
    
    // Validate form data
    if (in_array($submitted_value, $predefined_values)) {
        echo "Error: Invalid value submitted";
    } else {
        // Process form data
        // ... your code here
    }
}

Keywords

form validation prevent submission pre-defined values PHP validation error

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