How to prevent form hijacking in PHP?

I have had a lot of success by rendering the first line of the code (the form activation line) in javascript... eliminates the need for a captcha.

< .....script..... >
document . write (' < form action="page.php" method="get" > ' ) ;
<..... /script..... >

wrapped in javascript like the above line, it will only show to actual live users.

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I had to put a bunch of extra spaces in the above code for the system to let me post it. If you have a basic understanding of coding, you'll figure out what I did.