Fatal error: Call to undefined function mcrypt_encrypt()
We will get this fatal error of missing library, while moving prestashop website to new hosting server or new server. There are two ways to solve this problem. Either we need to create / edit php.ini with below lines.
Or you need to disable cipher algorithm until this library get installed on your server.
Execute the below SQL statement in your database to disabled to cipher algorightm, then prestashop will stop using mcrypt_encrypt library then your problem will be solved immediately.
UPDATE `ps_configuration` SET `value` = '0' WHERE `ps_configuration`.`name` = 'PS_CIPHER_ALGORITHM';