preventing duplicate submission code error

Hello everyone, ideas and help needed!

I want to prevent duplicate email submissions to the CF7. So I followed instructions from https://cfdbplugin.com/?page_id=904 but get an error when entering any email to the CF7 form:

Shortcodes, Actions and Filters Plugin: Error in user-provided code item named “Preventing Duplicate Submissions from CF7 2”.
syntax error, unexpected ‘$fieldName’ (T_VARIABLE)

My code is:

function is_already_submitted($formName, $fieldName, $fieldValue)
{
require_once(ABSPATH . ‘wp-content/plugins/contact-form-7-to-database-extension/CFDBFormIterator.php’);
$exp = new CFDBFormIterator();
$atts = array();
$atts[‘show’] = $fieldName;
$atts[‘filter’] = “$fieldName=$fieldValue”;
$atts[‘unbuffered’] = ‘true’;
$exp->export($formName, $atts);
$found = false;
while ($row = $exp->nextRow()) {
$found = true;
}
return $found;
}
function my_validate_email($result, $tag) {
$formName = ‘cf7form’; // Change to name of the form containing this field
$fieldName = ‘emailfield’; // Change to your form’s unique field name
$errorMessage = ‘ERROR MESSAGE HERE’; // Change to your error message
$name = $tag[‘name’];
if ($name == $fieldName) {
if (is_already_submitted($formName, $fieldName, $_POST[$name])) {
$result->invalidate($tag, $errorMessage);
}
}
return $result;
}
add_filter(‘wpcf7_validate_email*’, ‘my_validate_email’, 10, 2);

any ideas what’s wrong?
Thank you!