Is there a way to attach an image to an html formatted email message created in PHP?
We need to ensure that a corporate logo is on emails sent to clients who may not
There are more than enough answers here that should help fix your specific problem, but I just thought it might be worth pointing out that you may well have a larger problem that you hadn't considered.
Specifically - writing emailers to be sent via PHP is filled with potential gotchas and should only be done if you have a really good idea of what can go wrong.
If you're planning on sending emails fairly intensively I would strongly suggest doing it through either a dedicated email marketing client or implementing one of the many email marketing API's out there that will send it for you. (mailchimp is apparently a decent one).