latest release version of PHP4.
a. Obtaining and compiling PHP4
+
+ SquirrelMail has not been tested for use with PHP 4.3.x. The
+ development team does not recommend the use of this software with
+ PHP 4.3.x until further testing can be done.
Point your favorite webserver at http://www.php.net/version4/ and
download the source. Untar (tar xvfz filename-you-downloaded.tgz)