command line alias inside php exec

Question

Is there any possibility to define shell alias for commands executed via php system, exec etc functions? I'm running multiple versions of PHP using fastcgi and I need to run the right version of PHP when I execute

exec('php -f script.php');

inside web application, so for some vhosts calling php I need to run /usr/bin/php and for others e.g. /opt/php5.2.4/bin/php.

My virtual vhost configuration looks like this

    <IfModule mod_fastcgi.c>
        AddHandler php5-fcgi .php
        Action php5-fcgi /php5-fcgi
        Alias /php5-fcgi /var/www/test.loc/www.test.loc/cgi-bin/php52.fcgi
    </IfModule>

And php52.fcgi (php55.fcgi respectively):

#!/bin/sh
export PHP_FCGI_CHILDREN=4
export PHP_FCGI_MAX_REQUESTS=200
export PHPRC="/opt/php5.2.4/php.ini"
exec /opt/php5.2.4/bin/php-cgi

So every vhosts has it's own php5x.fcgi script and php.ini file.