Store Locator Plus Example show_search_form Hook

functions.php

/*base function*/
function slp_show_search_form(){
	$showSearchForm = true;

	$showSearchForm = apply_filters( 'slp_modify_show_search_form', $showSearchForm );

	$result = "";
	if($showSearchForm){
		//show the form
		$result = "some html";
	}

	return $result;
}

/*example developer implementation*/

//modify the $showSearchForm variable
function slp_modify_show_search_form_filter($showSearchForm){
	return false;
}

//add the filters
add_filter( "slp_modify_show_search_form", "slp_modify_show_search_form_filter" );

For testing purposes you can remove the return $result; and replace it with echo $result;