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PHP (a recursive acronym for PHP: Hypertext Preprocessor) is one of
the easiest ways to get started building web applications. PHP uses a
template strategy, embedding its instructions in HTML documents,
making it easy to integrate logic with existing HTML frameworks. PHP
does all this neatly and ingeniously. No doubt it has its dusty
corners, but the normal cycle of HTML form 
client
data database returned data
should be straightforward.
PHP was created with web use explicitly in mind, which has eased a number of issues that trip up other environments. The simple syntax is based on C with some Perl, making it approachable to a wide variety of developers. PHP is relatively new, but it is also focused and small, which reduces the amount of churn.
There do seem to be an unusual number of security alerts about PHP. Versions prior to 4.2.2 have a serious hole allowing an intruder to execute an arbitrary script with the permissions of the web server. This could be alarming, but if you have followed our advice about webuser and webgroup, it will not be much of a problem.
You might think that since your CGI scripts are, in effect, part of the HTML you send to clients, the Bad Guys might thereby learn more than they should. PHP is not as silly as that and strips its code before sending the pages out onto the Web.
Installing PHP proved to be very simple for us. We went to http://www.php.net and selected downloadsand got the latest release. This produced the usual 2MB of gzipped tar file.
When the software was unpacked, we dutifully read the INSTALL file. It offered two builds: one to produce a dynamic Apache module (DSO), which we didn't want, since we try to keep away from DSO's for production sites. Anyway, if you use PHP at all, you will want it permanently installed.
So we chose the static version and put the software in /usr/src/php/php-4.0.1p12 (of course, the numbers will be different when you do it). Assuming that you have the Apache sources, have compiled Apache, and are using MySQL, we then ran:
./configure --with-mysql --with-apache=../../apache/apache_1.3.9 --enable-track=vars make make install
We now moved to the Apache directory and ran:
./configure --prefix=/www/APACHE3 --activate-module=src/modules/php4/libphp4.a make
This produced a new httpd, which we copied to /usr/local/sbin/httpd.php4. It is then possible to configure PHP by editing the file /usr/local/lib/php.ini. This is a fairly substantial file that arrives set up with the default configuration and so needs no immediate attention. But it would be worth reading it through and reviewing it from time to time as you get more familiar with PHP since its comments and directives contain useful hints on ways to extend the installation. For instance, Windows DLLs and Unix DSOs can be loaded dynamically from scripts. There are sections within the file to configure the logging and to cope with interfaces to various database engines and interfaces: ODBC, MySQL, mSQL, Sybase-CT, Informix, MSSQL.
All that remains is to edit the Config file (see site.php):
User webuser Group webgroup ServerName www.butterthlies.com DocumentRoot /usr/www/APACHE3w/APACHE3/site.php/htdocs AddType application/x-httpd-php .php
This was a very simple test file in .../htdocs:
<HTML><HEAD>PHP Test</HEAD><BODY> This is a test of PHP<BR> <?phpinfo( )?> </BODY></HTML>
this is the magic line:
<?phpinfo( )?>
When run, this produces a spectacular page of nicely formatted PHP environment data.
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| 14.6. Apache v2: SSI Filters |  | 15.2. Site.php |
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