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/**
 * Adds form title to a data attribute on the form element
 * @param  [string] $form_tag The string containing the <form> tag
 * @param  [object] $form     The current form
 * @return [string]           The new <form> tag string
 */
function gravity_form_tag($form_tag, $form) {
    $form_title = $form['title'];
    $form_tag = str_replace('<form', "<form data-formtitle='{$form_title}'", $form_tag);
    return $form_tag;
}

add_filter('gform_form_tag', 'gravity_form_tag', 10, 2);