Convert any input type text field to tags field. You can write tags and move focus out of the text area to convert the value in tags.
$pdocrud = new PDOCrud();
$pdocrud->formFields(array("membership_categories"));
$pdocrud->addPlugin("bootstrap-tag-input");//to add plugin
$pdocrud->fieldAttributes("membership_categories", array("data-role"=>"tagsinput"));
$pdocrud->fieldCssClass("membership_categories", array("tagsinput"));// add css classes
echo $pdocrud->dbTable("library_membership")->render();
echo $pdocrud->loadPluginJsCode("bootstrap-tag-input",".tagsinput");//to add plugin call on .tagsinput class