How can I retreive SiteID via API with site url

Is there a simple method of getting the SiteID when I only know the site URL using an PHP API ?

Why do you not know the siteid? That should be something you know, look in websites under settings. I am pretty sure the API does not allow you to search for a siteid.

Yes it does,

Use SitesManager.getSitesIdFromSiteUrl (url)