digital sugnatures, php, and shell :-)

[Meni]

Hello everyone.

I have a web service that can (also) email documents to clients.

I want to be able to digitally sign documents in order to email them signed as proof of correct content.

I am looking for a way to sign these documents.

The documents are currently in HTML format but may be converted to PDF / DOC format in the future.

The web service is written in PHP and i have access to shell, so i figure either there's a way to sign files with PHP, or I have to run system() command with php and sign as if I am signing from shell.

Everything is on Debian Etch, Apache and MySQL.

Can anyone help?
Thanks.

[sjau]

Have a look here: http://www.pantz.org/scripting/php/gpgemail.shtml

Furthermore google for "PHP GPG " --> that will result it many hits.