Help with a PHP API integration setup

I need to create a form that checks if an email address exists on a list, whether it be a subscribe, unsubscribe or suppressed list. If the email does not exist, add it to a list, if it does exist, show error with words "this email address is used on (name of list)."

Can anyone help? Or write (QUOTE)? License (Only if you have a working version that you use)? Or let me know if I can download or install on a server the appropriate script for this please? Quotes will be accepted however please note that this is not a project set, meaning, I do not have the approval to make this a billable project, so this is not spec work. If you have links that you are willing to share, i would greatly appreciate.

Thank you very much!

Frederick Polk, One Black Crayon

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