PHP将变量传递给系统（'zipcloak'）

Question

I have a task, the customer wants us to encrypt his zip files with a password. I use ZipArchive in php to generate the zip files, but the server runs php 5.5 and my boss doesn't want to upgrade yet. The customer needs the encrypted zip files and we can't postpone this anymore... The ZipArchive::setPassword() works only above 5.6. I'm trying to bypass it by calling system('zipcloak asd.zip');When I run it from terminal, it asks for the password. I'm curious if I can pass the user given password to the command as a variable or I need a better workaround for this. Thanks in advance.