Ajax & cron jobs Dr. Steven Bitner AJAX (Asynchronous - PowerPoint PPT Presentation

Ajax & cron jobs Dr. Steven Bitner

AJAX (Asynchronous JavaScript and XML)

So far in this course…  All of our interactions have been server side or client side  AJAX blurs the lines a bit

AJAX

Change out part of a page

Policy  Can only perform local AJAX calls  You can however override subdomain blocking  e.g. by defualt www.mysite.com cannot make AJAX calls to info.mysite.com but that setting can be changed.

First steps  First, you need JavaScript to create an object  jQuery can do this for you  Great because it handles cross browser issues related to the different object types in IE vs Chrome etc.  This object is an HTTP request object that goes to a specified url  in jQuery, via the ajax, load, get or post method – we'll talk about load since it is sufficient for all that we have learned

Load  For loading a web page directly into a page element  Requires result to be text or html $("button").click(function(){ $("#myDiv").load("mydiv.php"); });

Partial load  You can also load only a portion of the returned data $( "#myDiv").load("mydiv.php #someDiv");

Sending a GET type request  For loading a static page where no arguments are needed $("button").click(function(){ $("#myDiv").load("mydiv.php?" + "username=bitners" + "&show=Always Sunny in Philidelphia"); });

Sending a POST type request  For loading a static page where no arguments are needed $("button").click(function(){ $("#myDiv").load("mydiv.php", { username:"bitners", show:"Always Sunny in Philidelphia" }); });

Cron

Cron jobs  Some tasks just need to be completed regularly  Daily status report for your website  How many new users  How many downloads of particular files etc.  Weekly email blast to followers

Cron is the way  Linux/Unix has a built in utility for this  Controlled by a text file called crontab

Crontab fields Minute of execution 1. Hour of execution (24 hour) 2. Day of execution 3. Month of execution 4. Day of the week (0 => Sunday, 6 => Saturday) 5. File to run 6.

Crontab example line  30 0 * * * emailBlast  This would run the job at midnight thirty every day of every month  59 23 * * 0,6 weekend  This would run weekend every Saturday and Sunday at one minute before midnight  cd /home/faculty/bitners/public_html && mailer  To run a PHP script, must first call executable, e.g. /usr/bin/php mailer.php

Editing the crontab file  Just type `crontab – e` at the command prompt in puTTY  This will open the file for editing