Warning: file_put_contents(): unsuccessful to open stream: Permission denied

Hi we am new to Mac and web development..These days we am perplexing to do
a rudimentary web page with a rudimentary form with HTML and Javascript,
and a form will be processed by PHP. The PHP will be opening txt file,
review from and write to this txt file.The blunder summary comes from this
line of code.file_put_contents("order.txt", $content);and a blunder
summary is Warning: file_put_contents(order.txt): unsuccessful to open
stream: Permission denied in /Users/maoyang/Sites/3006/process.php on line
57all a HTML and PHP codes are in a myname/Sites/3006 folder of my
computer. we have finished some investigate and all of them tells me that
we need to change some settlement to make a txt record writeable, though
unequivocally really confused how to do so. Anyone know a good instruction
page we could follow(for mac environment).Thank we unequivocally much..