Follow the installation steps to install PHP on UNIX to the Apache module,

This occurs because the PHP module does not run smoothly for some reason. Before asking for help, check the following three steps:
Make sure that the httpd program you run is compiled. Run/path/to/binary/httpd-l. If you do not see mod_php3.c in the list, reinstall the Apache program.
Are you sure you are in the Apache configuration file. conf (such as httpd. conf), such as AddType application/x-httpd-php3. php3. Make sure that the above AddType is not in the <Virtualhost> or <Directory> region. Otherwise, the MIME type you added will be invalid.
Finally, because Apache 1.2.x and Apache 1.3.x have different system configuration files. You need to check which configuration file is and check whether the AddType type is added to PHP. You can put an incorrect configuration syntax in httpd. conf to check whether the configuration file is correct when running httpd.