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<?php

/**
* Limit IP to One Submission Per Time Period
* http://gravitywiz.com/2012/05/12/limit-ip-to-one-submission-per-time-period
*/
 
$gws_limit_message = 'You may only submit this form once every 24 hours.';
$gws_limit_time = 86400; // must be specified in seconds; 86400 seconds is equal to 24 hours
 
// update the "5" to your form ID
add_action('gform_pre_render_5', 'gform_limit_ip_submissions');
function gform_limit_ip_submissions($form){
    global $gws_limit_message, $gws_limit_time;     
    
    if(!gform_has_ip_exceeded_limit($form, $gws_limit_time))
        return $form;
    
    $submission_info = rgar(GFFormDisplay::$submission, $form['id']);
    
    // if no submission, hide form
    // if submission and not valid, hide form
    if(!$submission_info || !rgar($submission_info, 'is_valid')) {
        add_filter('gform_get_form_filter', create_function('', "return '<div class=\"limit-message\">$gws_limit_message</div>';") );
    }
     
    return $form;
}

add_filter('gform_validation_5', 'gform_validate_limit_ip_submissions');
function gform_validate_limit_ip_submissions($validation_result) {
    global $gws_limit_message, $gws_limit_time;
    
    if(gform_has_ip_exceeded_limit($validation_result['form'], $gws_limit_time))
        $validation_result['is_valid'] = false;
        
    return $validation_result;
}

function gform_has_ip_exceeded_limit($form, $limit_time) {
    global $wpdb;
    
    $current_ip = RGFormsModel::get_ip();
    $last_submission = $wpdb->get_var($wpdb->prepare("SELECT date_created FROM {$wpdb->prefix}rg_lead WHERE ip = %s and form_id = %d ORDER BY date_created DESC", $current_ip, $form['id']));
     
    if(empty($last_submission))
        return false;
     
    $time_out = strtotime($last_submission) + $limit_time;
    $current_time = time();
     
    return $current_time > $time_out ? false : true;
}