How to Use Oracle Cloud Infrastructure Email Delivery in Rest API and PHP Programming format

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I want to use Oracle Cloud Infrastructure Email Delivery REST API and create a domain name. But I am having trouble in making authorization and header. There is no clear instruction how to use authorization and header in Oracle Cloud Infrastructure REST API Web Page specially when I browse email delivery. https://docs.oracle.com/en-us/iaas/api/#/en/emaildelivery/20170907/EmailDomain/CreateEmailDomain

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I tried to use a PHP programming code to achieve what want but I still receive an error. Here is my PHP code