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

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