A script that will pre populate fields in my custom HTML templates

General information for the website: I am selling custom html templates
Description of requirements/features: So what I need is a script that I can use for pre populating fields within HTML code.

I offer clients HTML templates however they have no knowledge of editing HTML code, so this script will need to be a type of form where they fill out the title, description etc and then press generate HTML which will supply the html code which they can then copy and paste.

I will need to know how to adapt this script to other templates I make specific for each client so it must be easily adaptable. Ideally I will want to be able to use some type of tags to determine editable fields. I know HTML and a little PHP so this shouldn't be much of a problem if I am shown. (documentation must be provided)

The types of fields I will need are

- Single input field (for fields such as Title, Sub title, Price)
- Text area field (for content that is not styled)
- WYSIWYG editor field (for descriptions and long text pieces where the client can choose to underline text, make text bold etc)
- Image upload to folder in FTP (I will need to change the folder destination for each client)

I also want the option to set a default value in certain fields so that the client does not need to go back each time and edit the fields that normally will stay the same.
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