I am sure that you cannot load two versions of PHP in apache at the same time. However, you can use two different versions of PHP using mod_fcgid.
Windows, , .
FastCGI PHP http://fuzzytolerance.info/blog/apache-mod_fcgid-and-php-on-windows/
, .
FCGI , VirtualHost
:
<VirtualHost *:80>
  ServerName site1
  ServerAdmin admin@site1
  DocumentRoot "c:/www/site1"
  <Directory "c:/www/site1/web">
    Options +ExecCGI
    AllowOverride All
    
    AddHandler fcgid-script .php
    FcgidInitialEnv PHPRC "c:/php52"
    FcgidWrapper "c:/php52/php-cgi.exe" .php
    AddType application/x-httpd-php .php
    Order allow,deny
    Allow from all
  </Directory>
</VirtualHost>
FcgidInitialEnv PHPRC, , php.ini, FcgidWrapper php-cgi.exe PHP.
VirtualHost, PHP. PHPRC , .
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