How do I add a checkbox to the performance page and have it repopulate? I would like to add a checkbox of my own to the performance page in the Drupal administration.  I am using hook_form_alter like this:

function nci_assay_depot_form_alter(&amp;$form, &amp;$form_state, $form_id){
    switch($form_id){
        case "system_performance_settings":
            $form["caching"]["nci_assay_depot"] = array(
                "#type" =&gt; "checkbox"
                ,"#title" =&gt; "Refresh Assay Depot Cache when 'Clear All Caches'"
                ,"#default_value" =&gt; 1
                ,"#disabled" =&gt; 0
                ,"#description" =&gt; null
                ,"#weight" =&gt; -2
            ) ;
        break;
    }
}


It will display on the page, but the value will not be saved.  Any thoughts?
to have it "repopulate" after save provide a #default_value key that retrieves it on page load.
to actually save it append (add another) custom form submit handler to the form, after the original one gets fired. Something like $form['#submit'][] = 'mymodule_mysubmit_handler'; You will have to check where the submit handler is set already in the form, or the element you're trying to hook into (such as $form['caching'] ...