js alert in add_filter function for image_send_to_editor
You can try as like this, it may help you. function filter_image_send_to_editor( $html, $id, $caption, $title, $align, $url, $size, $alt ) { if(‘your error statement’) { $html=”<script>alert(“Some Error Message”)</script>”; } else { //your continue code } return $html; }; // add the filter add_filter( ‘image_send_to_editor’, ‘filter_image_send_to_editor’, 10, 8 ); More Info Regarding image_send_to_editor Filter : … Read more