PHP image generation code and HTML mixed up with garbled

A section of PHP image generated code embedded in the HTML, PHP part of the appearance is garbled what is the reason?

Workaround: The code above results in a picture
Take this file as a separate PHP and use the tag in HTML to invoke it.

Direct insertion Of course is garbled, because the browser has been in the way of HTML to deal with, half of you to another picture format, of course not.

Call Method:

Use the time directly with HTML syntax: Call on it, in the server to do the validation of the session to store the validation characters compared to the user submitted characters, the same pass the verification