Unfortunately, computing is more like an art than it is a science and things go wrong. I know that's a shocker but it's true. As such, there are common problems you might encounter when installing PHP. What? You mean PHP isn't perfect?! Well, as a language it almost is, but installing it can be a bear for the inexperienced. So let's take a look at what might happen and try to keep that blood pressure down, will ya?
One of the more common mistakes is trying to compile PHP with a module when you haven't yet installed that module on your system. If you want to have GD support with PHP, you have to install the GD libraries on your system first. This may seem obvious, but even I have made this mistake. Probably the best place to find out where you can download modules for PHP is on the PHP site. Just go to the online manual and look for the section that concerns the module you'll be installing. There is usually a link to where you can download the latest supported version of that module right on the manual page.
On a Windows install of PHP, it's best to put your DLL's in the WINNT/ or WINDOWS/ directory. They may work in other locations, but they're sure to work in these directories. There's no accounting for a fickle OS.
Also on Windows, you usually need to put a copy of php.ini in the WINNT\ or WINDOWS\ directory even if you won't be changing anything. If you haven't done this, the problem may not be obvious just by viewing a web page which will probably be blank. You'll need to take a look at the appropriate error log for IIS or PWS.
When compiling PHP on Unix, be sure to do a make clean or make distclean before you start the configuration process.
Check permissions! If you don't have ownership of your Apache install directory, you won't be able to install PHP as an Apache module. For that matter, if you're not the root user, you're probably limited as to what you'll be able to do as far as installation goes. That goes out to all you virtual hosters out there.
On Apache, when you first install PHP, you'll probably need to make sure that Apache knows what to do with files ending in .php or .phtm or whatever. Edit the httpd.conf file and look for lines that look like this:
#AddType application/x-httpd-php .php
With a new Apache install, it should look just like this -- commented out. Uncomment that line and restart Apache and it should recognize .php files.
You will also need to get Apache to recognize index.php. By default, it only looks for index.html so you have to tell it otherwise. Whip that Apache configuration into shape! Look for a line that says:
DirectoryIndex index.html
And append index.php to the end of it.
DirectoryIndex index.html index.php
For post-installation troubleshooting, you should get familiar with the web server error log files. For Apache, this is usually the error_log file located in the logs/ directory of your Apache installation. For Windows, this should be in either WINNT\LogFiles\ or WINDOWS\LogFiles\. Anytime you have a problem that isn't immediately obvious, you should review your error log file and take a look at the last few lines.
One final note. The PHP manual is probably the best online manual around for any language. I recommend that you get very familiar with it because most of the problems that you might encounter are covered there. I also recommend subscribing to one or more of the mailing lists.
Darrell Brogdon
is a web developer for SourceForge at VA Linux Systems and has been using PHP since 1996.
