Autofill email input box in php
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i want to send certain emails to my clients and a link is provided in those emails(something like a activation email to active your account), when users click on that link they are directed to a page on my website , that page has a email input box.

I want that when they click on that link and get redirected to my site the input field should be automatically filled with email from where user has clicked the link.(note the user need not be signed in on my site)

Any way i can do this , im using PHP 

Thank you