Question about if/else if

[wrfan]

I don't quite understand how the "if/else if" stuff works.

I wrote this sample script:

 <?php
$myip = "127.0.0.1"; 
$googleuseragent = "Googlebot/2.1 (+http://www.googlebot.com/bot.html)";

if (getenv ("HTTP_X_FORWARDED_FOR")) 
{
$ip = getenv ("HTTP_X_FORWARDED_FOR");
}
else
{
$ip = getenv ("REMOTE_ADDR");
}
if ($ip==$myip)
{
echo "admin detected";
}
else if ($HTTP_USER_AGENT==$googleuseragent) 
{
echo "google detected";
}

?>

Then I changed my http_user_agent to Googlebot/2.1 (+http://www.googlebot.com/bot.html) using webwasher.com programme and executed the php script on my localhost server. Thus, both things are true - $ip==$myip AND $HTTP_USER_AGENT==$googleuseragent. How comes then, that the php script returns only the first of the statements as a true one? if ip is checked first, it returns "admin detected"; if I reverse the order in the script and http_user_agent is checked first, then "google detected" is returned. But since both statements are true, shouldn't the php script echo both statements, i.e. "admin detected" AND "google detected"?

[matt_4013]

That's how an elseif works. Probably the easiest way to figure it is to write the logic in grammatical english.

If $ip is equal to $myip, then echo "admin detected". If it's not (this is the else), then if $HTTP_USER_AGENT is equal to $googleuseragent, then echo "google detected".

An Elseif only checks the second condition if the first proves false. What you'll want to be doing there, is either just using another if, or nesting your second if inside the first one.

Hope that helps,
Matt

[wrfan]

thanx. basically what I want to do is to write a counter, that checks whether the visitor is a search engine or myself, if not, then the counter should be increased, otherwise stay the same:

if ($ip==$myip)
{
echo "admin detected";
}

else if ($HTTP_USER_AGENT==$googleuseragent) 
{
echo "google detected";
}

else if ($ip!==$myip)
{
connect to mysql, increase counter etc.
}

The thing that confused me is that for the search engine both statements are true - $HTTP_USER_AGENT==$googleuseragent AND $ip!==$myip. But since you say that "elseif" checks the second condition only if the first one proves false, then it's ok, isn't it? when php detects that $HTTP_USER_AGENT==$googleuseragent, it won't even move to the next condition (or to the next conditionS, if there are several ones), but will stop right there, right?

I know, in practice I could combine several conditions, but I just want to know whether such a script is ok.

[matt_4013]

Yeah, exactly. If either of the top 2 prove true, then it wont even look at the last one. I would do it like this:

if($ip == $myip) {

// If your the IP's are the same
echo "You're an admin!";

} elseif($HTTP_USER_AGENT == $googleuseragent) {

// If the user agent is a bot
echo "Ahh, a google bot!";
} else {

// If ANYTHING else

// Increment your counter
echo "Finally, a unique visitor!";
}

[wrfan]

Thanx 🙂