Help with PHP

What we require
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A method which does the following:

A method that we can pass in a POST ID, within this method it should then:

1. Query the database to see if that given post has been selected on any PAGE in the custom fields which have been setup.
2. If so, then the method then extracts the ID's of all the PAGES that the post has been selected in.
3. An array is returned of all the PAGE ID's, or if none are found an empty array is returned.


We then require a second method which does the following:

A method that we can pass in the PAGE ID, within this method it should then:

1. The title of the page will be gained.
2. The ID and title of all the POSTS which have been selected in all the sections (In the same order as the sections which are setup on the page in the admin.)
3. Return this data in whatever is the best way.