Lots of answers here and elsewhere on Google for how to setup your WAMP or XAMP on localhost to send emails.
However for testing/developing, you mostly don't care about emails actually getting transmitted. You just want to check how they're formed, and whether the email picked up the correct settings and options.
So, I remember having this problem a few months ago and finding a solution/service which did this:
As soon as my PHP code triggered an outgoing email, it would present it as a real draft email in a new window in my email client (Outlook, as it happens). I could check the from/to/subject/body instantly and easily. Nothing actually got transmitted, and I didn't have to keep a bunch of inboxes open somewhere or worry about delays or junk folders.
Trouble is I can't remember how I set this thing up. It was either a service which I downloaded and installed or it was a tutorial on how to set this up in WAMP. It was possibly a WordPress plugin but I'm not sure. I am certain it was free.
Does anyone recognise this kind of setup for email testing in PHP?
Are you sure it is a PHP configuration and not a software?
I used a mail smtp 'catcher' that works as you describe.
I hope it could be useful for your interests: Test Mail Server Tool (http://www.toolheap.com/test-mail-server-tool/)