getenv() question- why?

madcat

I was hoping someone could explain this to me...

In my books example, it says to use getenv() to be sure that you're reading the correct value and to assign a value to a variable of your choice.

Ok, but I am able to assign a value to a variable just fine without using getenv - how does this help? How does this help to read the correct value?

In the first example I use getenv() but it doesn't give me the output I was looking for...why doesn't it work?

<?php
$address = getenv($_SERVER['REMOTE_ADDR']);
echo "Your IP address is $address.";
?>

Your IP address is .

<?php
$address = $_SERVER['REMOTE_ADDR'];
echo "Your IP address is $address.";
?>

Your IP address is 127.0.0.1.

Hope you can tell what I'm talking about...Just wondering why it is important to use getenv and why it's not working in the example above. I'm gonna read what other people had to say about it at php.net too😉

Thanks for any help!

ednark

here is your problem, getenv() takes a string, the name of the variable, not the actual $variable itself

you need:

<?php
$address = getenv('REMOTE_ADDR');
echo "Your IP address is $address.";
?>

read more at:
http://www.php.net/manual/en/function.getenv.php

detailed explaination:

<?php
$address = getenv($_SERVER['REMOTE_ADDR']);
echo "Your IP address is $address.";
?>

first php interprets your $ variables on the right of =.
It will look in $_SERVER for 'REMOTE_ADDR'.

so you then get

<?php
$address = getenv(127.0.0.1);
echo "Your IP address is $address.";
?>

then it will hit your getenv: it will not find a variable called '127.0.0.1' so will return an empty or NULL value, which it is failthfully printing in your results..

<?php
$address = NULL;
echo "Your IP address is $address.";
?>

when it gets around to evaluating $address you will get

<?php
echo "Your IP address is .";
?>

and print

'Your IP address is .

madcat

Thanks- your explanation makes sense to me however:

<?php
$address = getenv('REMOTE_ADDR');
echo "Your IP address is $address.";
?>

produces...

Your IP address is .

The example above is how they have it at php.net too.

Using:

<?php
$address = $SERVER['HTTP_USER_AGENT'];
echo "Your IP address is $address.";
?>
OR...
<?php
$address = $SERVER['REMOTE_ADDR'];
echo "Your IP address is $address.";
?>

Work correctly- so are they wrong to use? Just a bit confusing when trying to learn is all- thanks again for your help.

ednark

that is wierd:

getenv('REMOTE_ADDR') works both on my winXP box and my linux 7.1 box, both running 4.2.2 and Apache.

maybe you have some funky php.ini settings: im not sure about this but a quick look at php.ini shows that perhaps these might affect getenv()'s functionality

variables_order
safe_mode_allowed_env_vars
safe_mode_protected_env_vars