missing mcrypt php extension

apt-get install php5-mcrypt
php5enmod mcrypt

edit  /etc/php5/apache2/php.ini

 #add below line  
 extension=mcrypt.so  

ls -l  /etc/php5/apache2/conf.d

 20-mcrypt.ini -> ../../mods-available/mcrypt.ini  
 05-opcache.ini -> ../../mods-available/opcache.ini  
 10-pdo.ini -> ../../mods-available/pdo.ini  
 20-gd.ini -> ../../mods-available/gd.ini  
 20-json.ini -> ../../mods-available/json.ini  
 20-mysql.ini -> ../../mods-available/mysql.ini  
 20-mysqli.ini -> ../../mods-available/mysqli.ini  
 20-pdo_mysql.ini -> ../../mods-available/pdo_mysql.ini  
 20-readline.ini -> ../../mods-available/readline.ini  

restart apache2 with
# service apache2 restart

done