two ?s: '' vs ""; function to post form data

Hello, I have two newbie-ish questions. 1. I've been reading a few php articles today, and so far I've not come across a clear distinction between variables defined using '' and those using "". I've read those are both strings, but what is the difference? 2. If I know the right variable names, is there a function in PHP to post form data to another server? For example, if there was a form on example.com and I wanted to capture its html output, and it uses the post method, and I know the variable names in that form, is there a way to do the transaction using PHP? Thanks. Alan

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