Errors and Debugging

JavaScript

When developing JavaScript you will want to make use of the "JavaScript console" window, which is generally provided by your browser, to retrieve helpful information about errors in your scripts. Useful browser add-ons are also available, such as Firebug for Firefox.

PHP

Although PHP is a programming language designed especially for use in a web context, you can still test your scripts at the command line in much the same way you do with Perl. That is, you can enter the command

php script.php

and check the output to see if you're getting what you expected. You need to remember, however, that the PHP code in your script file needs to be enclosed in the <?php ... ?> delimiters so that the interpreter will recognize it for what it is, namely actual PHP code.

PHP also has an error_reporting() function that allows you to set the "error reporting level". For example, the function call

error_reporting(15);

placed at the beginning of your script will cause the interpreter to inform you whenever reference is made to an unbound variable.

Perl

Perl is an "ordinary" programming language so you can (and you will want to) test your scripts at the command line before firing them up in your browser and/or placing them online. You can do this with a command like

perl -cw script.cgi

which tells the interpreter to (c)ompile without running and to provide any necessary (w)arnings about your script.