[php] Why are my PHP files showing as plain text?

I've been writing PHP applications using PHP for a while in WAMP. Now I'm installing PHP and Apache HTTP Server separately on my work PC. I've installed PHP 5, and the latest Apache. I go to localhost and see it works!

Now I add a file called test.php which displays:

<?php
    phpinfo();
?>

But in the browser it just displays plain text. Is there somewhere I have explicitly tell it to use PHP 5?

You need to configure Apache (the webserver) to process PHP scripts as PHP. Check Apache's configuration. You need to load the module (the path may differ on your system):

LoadModule php5_module "c:/php/php5apache.dll"

And you also need to tell Apache what to process with PHP:

AddType application/x-httpd-php .php

See the documentation for more details.

You might also, like me, have installed php-cgi prior to installing Apache and when doing so it doesn't set up Apache properly to run PHP, removing PHP entirely and reinstalling seemed to fix my problem.

You will need to add handlers in Apache to handle php code.

Edit by command sudo vi /etc/httpd/conf/httpd.conf

Add these two handlers

  AddType application/x-httpd-php .php
  AddType application/x-httpd-php .php3

at position specified below

<IfModule mime_module>

 AddType application/x-compress .Z
 AddType application/x-gzip .gz .tgz

--Add Here--


</IfModule>

for more details on AddType handlers

http://httpd.apache.org/docs/2.2/mod/mod_mime.html

Are you using the userdir mod?

In that case the thing is that PHP5 seems to be disabling running scripts from that location by default and you have to comment out the following lines:

<IfModule mod_userdir.c>
    <Directory /home/*/public_html>
        php_admin_flag engine Off
    </Directory>
</IfModule>

in /etc/apache2/mods-enabled/php5.conf (on a ubuntu system)

You should install the PHP 5 library for Apache.

For Debian and Ubuntu:

apt-get install libapache2-mod-php5

And restart the Apache:

service apache2 restart

Yet another reason (not for this case, but maybe it'll save some nerves for someone) is that in PHP 5.5 short open tags <? phpinfo(); ?> are disabled by default.

So the PHP interpreter would process code within short tags as plain text. In previous versions PHP this feature was enable by default. So the new behaviour can be a little bit mysterious.