The Yeti package allows web developers to offer content in any language without having multiple copies of their scripts to code and maintain. Check out this sample page. You will need help from people who can translate (like your client's overseas agents), but you need no linguistic skills at all and they need no understanding of HTML, php etc.. You need to have your website on a server that runs php and can use utf-8 encoding. Save this test page and upload to your server to check that you see characters like these Japanese ones: 日本語
Yeti is free to download (1 Mb .zip) and deploy under the GNU License.
Though easy to customise, the installation should work "straight out of the box".
PAYMENT: Yeti is FREE. Please do NOT send donations to the author or to his Gay Pal. If you add this package to a commercial site, you might donate to a good cause (a registered charity or your kid's college fund etc.) at least 1% of whatever you charge your client.
Please send any bug reports and news (urls) of websites using this to yeti@yowsie.com.
The author knows of no similar software packages. If there are any, then any resemblances are totally co-incidental.