Apache: The Definitive Guide, 3rd Edition

Errors

If you make a syntax error, say by including a } after the printf() line, you get a sensible error message on the browser:

Parse error: parse error in /usr/www/APACHE3/site.php/htdocs/lookup2.php on line 25

However, syntax errors are not the only ones. We wanted to leave the previous examples simple, to illustrate what is happening. In real life you have to deal with more sinister errors. PHP has a syntax derived from Perl:

mysql_connect("127.0.0.1","webserv","") or die(mysql_error());
mysql_select_db("people")  or die(mysql_error());

The function die() prints a message — or executes a function that gets and prints a message and then exits. If, for instance we try to select the nonexistent database people2, the function mysql_select_db( ) will fail and return 0. This will invoke die( ), which will run the function mysql_errr( ), which will return the error message generated by MySQL inserted into the HTML. So, on the browser we have the following:

Lookup: You want people called jane
We have: Unknown database 'people2'

In development you should use or die() wherever something might not happen as planned.

However, when the pages are visible to the Web and to the Bad Guys, you would not want so revealing a message made public. It is possible (though too complicated to explain here) to define your own error handler. You might have a global variable — say $error_level is set to develop or live as the case may be. If it is set to develop, your error handler would invoke die(). If it ...