You may want to check the reply I made on your previous post.
The array $_GET basically just tells the server to get a variable from the url bar and the name of that variable goes between the two brackets. So say for example the address is as follows: http://www.daniwebs.com/forums/newreply.php?do=postreply&t=14773
Then to get the variable 'do' you would use the following code to print/echo/display it to the browser:
So the $_GET array and any other array beginning with $_ (dollar sign then underscore) is a inbuilt function.
As for the default value, there is no default value as it only holds the values that are in the url bar.
But I hv a doubt. How can i check whether there are any value in url bar or empty. I mean how can i check there is a value in url or not. If there only address in url bar, then what is the value of _GET?
Well $_GET should always have quotation marks between the brackets and numbers/letters/characters between the quotation marks. So $_GET on its own isn't a valid command. You need something like $_GET or $_GET and if it does not exist in the url bar then it will return a string with 0 letters 0 numbers and 0 characters. So basically a $_GET statement which has letters between the brackets and quotation marks but those letters/variable does not exist in the url bar will return the below string if you remove the quotation marks:
"" - as you can see there is nothing between those quotation marks so you will just receive a blank string if it does not exist in the url bar.
So just a reminder, you always need something between those brackets (more than just quotation marks).
I just saw more of what you are asking for and to check if there is nothing there i prefer to use the preg replace function just like follows:
//code in here
The preg replace should be something along those lines.