在我的情况下，php模块没有加载。试试这个:

检查加载了哪些模块:apache2ctl -M。查找类似php7_module (shared)的模块 如果没有列出php模块，则尝试加载与您的php版本对应的模块。在我的例子中，php包是libapache2-mod-php7.3。所以我这样做了:a2enmod php7.3，问题就解决了。

你只是把php文件打开到浏览器。你必须使用localhost url打开它。如果您直接从目录中打开一个文件，在任何情况下它都不会执行PHP代码。

使用:http://locahost/index.php或http:127.0.0.1/index.php

启用php短代码。在本例中，您使用<?这是<? PHP的PHP短代码。默认情况下，php短代码是禁用的。

如果你是ubuntu用户，也可以使用:sudo apt-get install php5 libapache2-mod-php5 php5-mcrypt。

听起来你的配置好像有问题，下面是一些你可以检查的东西:

Make sure that PHP is installed and running correctly. This may sound silly, but you never know. An easy way to check is to run php -v from a command line and see if returns version information or any errors. Make sure that the PHP module is listed and uncommented inside of your Apache's httpd.conf This should be something like LoadModule php5_module "c:/php/php5apache2_2.dll" in the file. Search for LoadModule php, and make sure that there is no comment (;) in front of it. Make sure that Apache's httpd.conf file has the PHP MIME type in it. This should be something like AddType application/x-httpd-php .php. This tells Apache to run .php files as PHP. Search for AddType, and then make sure there is an entry for PHP, and that it is uncommented. Make sure your file has the .php extension on it, or whichever extension specified in the MIME definition in point #3, otherwise it will not be executed as PHP. Make sure you are not using short tags in the PHP file (<?), these are not enabled on all servers by default and their use is discouraged. Use <?php instead (or enable short tags in your php.ini with short_open_tag=On if you have code that relies on them). Make sure you are accessing your file over your webserver using an URL like http://localhost/file.php not via local file access file://localhost/www/file.php

最后，查看PHP手册以获得更多的设置技巧。

尝试重新启动apache服务器。这就是我犯的错误——在安装php后忘记重新启动服务器!

service httpd restart

刚刚花了几个小时试图让PHP 5与Windows 10上的Apache 2.4一起运行。最后对我来说，这是httpd.conf LoadModule中的一个拼写错误。通过denny2018这个apachelounge线程的最后一个回答，提请注意写作和准确的模块路径。谢谢你！

过了两晚，我发现……我的目录是c:(小写)

我有LoadModule php5_module“c:/php/php5apache2.dll”，但正确的apache 2.4是:

LoadModule php5_module "C:/php/php5apache2_4.dll"

所以我之前也错过了_4(对于apache 2.4)。对我有用的完整片段:

# PHP
LoadModule php5_module "C:/php/php5apache2_4.dll"
AddHandler application/x-httpd-php .php
<FilesMatch \.php$>
    SetHandler application/x-httpd-php
</FilesMatch>

刚试过PHP 7。在Apache 2.4的httpd.conf中读取LoadModule行

LoadModule php7_module "C:/php/php7apache2_4.dll"

目前php手册显示c:/php/php5apache2.dll，当然需要调整。

在尝试了所有方法之后，我想出了这个解决方案

当默认情况下PHP 7.0 FPM未启用时，将出现此错误。

要在Apache2中启用PHP 7.0 FPM，运行:

 sudo 2enmod proxy_fcgi setenvif
 sudo a2enconf php7.0-fpm
 systemctl restart apache2

如果您使用的是php7.4，在上面的命令中输入7.4而不是7.0。