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Getting Started With Functions

Tim Perdue

Functions are interesting animals in PHP. Functions are kind of like "black boxes" since they cannot see outside of their universe and you cannot see inside of them. That's a bit different than some other languages I've programmed in. In some languages, a function would be able to see "global variables", but in PHP they cannot unless you specifically set it up that way. 


function my_function ($string, $int) {

global $REMOTE_ADDR;

echo $string."<P>";
echo $int."<P>";
echo $REMOTE_ADDR;

}

And there you have it. Because I specifically declared $REMOTE_ADDR to be a global variable inside this function, I can now see it and echo it as if it were a local variable. I cannot have access to global variables like $HTTP_USER_AGENT in that function, since I did not declare it.

To call this function, I simply say: 


my_function ("PHPBuilder.com", 1);

And it will echo:

PHPBuilder.com

1

127.0.0.1

I use functions for commonly-used code in my pages. It's cleaner than simply using include to include the same code over and over, although both will work. One very interesting use for functions is to build common features on an HTML page, like your headers/footers. 


function site_header ($title) {

?>

<HTML><HEAD><TITLE><?php echo $title; ?></TITLE></HEAD>
<BODY>
...more HTML....

<?php

}

function site_footer() {

?>

...more HTML...

</BODY></HTML>

<?php

}

There's a whole lot more that you can do with functions, and I won't mention it all here. This should be enough to get you up and running.