PHP's print_r function allows you to dump out the contents of a variable - and that includes more complex variables like arrays containing other arrays, objects, etc ... in a human (programmer!) readable form. By default, the output string is directly sent to the browser, but with a second parameter that's a true value, it is returned to you for further processing.

Here's an example of print_r's output being decorated to allow for special characters and to retain the spacing so that it can be displayed via the browser:

<?php print ("<pre>".htmlspecialchars(print_r($_SESSION,1))."</pre>"); ?>

And here is a sample of that running in our session demonstration:


(run the demonstration here with that extra trace line now added; you'll find that our wrapper is maintaining your session history too, but that's another story!)

This is a particularly useful facility to use if you're debugging a multipage application and want to see how the data is passed from one page to another.

Remember - if you alter the PHP script that's running a multipage application, you'll probably need to delete the session cookie too ... otherwise you will have changed the program but your testing would continue with the old data!
(written 2009-07-09)

 H310 - PHP - Putting it all together
  [3454] Your PHP website - how to factor and refactor to reduce growing pains - (2011-09-24)
  [2931] Syncronise - software, trains, and buses. Please! - (2010-08-22)
  [2635] A PHP example that lets your users edit content without HTML knowledge - (2010-02-14)
  [1962] Index Card System for Game Characters in PHP - (2008-12-27)
  [1840] Validating Credit Card Numbers - (2008-10-14)
  [1794] Refactoring - a PHP demo becomes a production page - (2008-09-12)
  [1754] Upgrade from PHP 4 to PHP 5 - the TRY issue - (2008-08-15)
  [1716] Larger applications in PHP - (2008-07-22)
  [687] Presentation, Business and Persistence layers in Perl and PHP - (2006-04-17)
  [468] Stand alone PHP programs - (2005-10-18)

Back to PHP preg functions - examples and comparision

Previous and next or Horse's mouth home

Forward to Who is Marc Schneider of Multilingual Search Engine Optimization Inc

Understanding the new local government structure in Wiltshire
First courses for 2010
Python classes / courses - what version do we train on?
Who is Marc Schneider of Multilingual Search Engine Optimization Inc
Debugging multipage (session based) PHP applications
PHP preg functions - examples and comparision
Three recent questions on Tomcat Convertors
Monitoring and loading tools for testing Apache Tomcat
Dogs Trust, Dog Show, Newbury
Wiltshire - a chance to improve life for everybody