How can one avoid PHP errors related to constants when using $_REQUEST[ ]?

When using $_REQUEST[] to access form data in PHP, it's important to check if the constant is defined before using it to prevent errors. One way to avoid PHP errors related to constants is to use the defined() function to check if the constant exists before accessing it through $_REQUEST[]. 

if (isset($_REQUEST['form_field']) && defined($_REQUEST['form_field'])) {
    $value = $_REQUEST['form_field'];
    // Use $value here
} else {
    // Handle the case where the constant is not defined
}

Keywords

PHP constants $_REQUEST error handling validation

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