Processwire - example of how to use fields to automatically create page name and title, including date fields and page ID..

buildUrl.module

<?php
class BuildUrl extends WireData implements Module {

    /**
    * Basic information about module
    */
    public static function getModuleInfo() {
	    return array(
		   'title' => 'Build URL',
		   'summary' => 'Builds a URL on page save based on specific fields.',
		   'href' => '',
		   'version' => 001,
		   'permanent' => false,
		   'autoload' => true,
		   'singular' => true,
	    );
    }


    /**
    * Populate the default config data
    *
    */
    public function __construct() {

    }

    /**
    * Initialize the module and setup hooks
    */
    public function init() {
	   $this->pages->addHookAfter('saveReady', $this, 'buildUrl');
    }

    /**
    *
    * @param HookEvent $event
    */
    public function buildUrl(HookEvent $event) {
	   // Accesses the $page object

	   $page = $event->arguments[0];
	   //if(!$page) return;
	   
	   if($page->template != 'session') return;
	   if($page->semester == '') return;
   		
	   		
	   		// NAME
	   		
	   		$pageName = '';
	   		
	   		// Semester, Class, Instructor
	   		$pageName .= $page->semester->name . '-';
	   		$pageName .= $page->class->name . '-';
	   		if(count($page->session_instructors)) {
	   			$pageName .= $page->session_instructors->first()->name . '-';
	   		}
	   		
	   		
	   		// Days & Times
	   		$dayName = $page->session_day->name;		
	   		$dateName = '';
	   		$sidName = '';
	   		
	   		if($page->sem_start && $page->sem_end) {
	   			$dateName = '-' . date("m d y", $page->getUnformatted("sem_start")) . '-' . date("m d y", $page->getUnformatted("sem_end")) . '-';
	   			$sidName = '-id' . $page->id;
	   			$dayName = '';
	   		}
	   		
	   		if($page->date) {
		   		$dateName = date("m d y", $page->getUnformatted("date")) . '-';
		   		$sidName = '-id' . $page->id;
		   		$dayName = '';
	   		}
	   		
	   		$pageName .= $dayName . $dateName . $page->time_start . $sidName ;
	   		
	   		
	   		// TITLE
	   		
	   		$pageTitle = '';
	   		
	   		// Semester, Class, Instructor	   		
	   		$pageTitle .= $page->semester->name . ' - ';
	   		$pageTitle .= $page->class->title . ' - ';
	   		if(count($page->session_instructors)) {
	   		$pageTitle .= $page->session_instructors->first()->title . ' - ';
	   		}
	   		
	   		
	   		// Days & Times

	   		$dayTitle = $page->session_day->title . ' ';		
	   		$dateTitle = '';
	   		$sidTitle = '';
	   		
	   		if($page->sem_start && $page->sem_end) {
	   			$dateTitle = ' ' . date("m d y", $page->getUnformatted("sem_start")) . '-' . date("m d y", $page->getUnformatted("sem_end")) . ' | ';
		   		$sidTitle = ' ID: ' . $page->id;
		   		$dayTitle = '';
	   		}
	   		
	   		if($page->date) {
		   		$dateTitle = date("m d y", $page->getUnformatted("date")) . ' | ';
		   		$sidTitle = ' ID: ' . $page->id;
		   		$dayTitle = '';
	   		}
	   		
	   		$pageTitle .= $dayTitle . $dateTitle . $page->time_start . $sidTitle ;

	   		$page->name = $pageName;
	   		$page->title = $pageTitle;
		   
		   $this->message("slug changed to " . $page->name);
		   $this->message("title changed to " . $page->title);

    }
}