[help]a simple question

i am a newbie of php,maybe this is a simple and a little silly question,but i want to know the true principle of it.hope someone can help me .
Q:
there is a function,and have a form like this $a->b in a function bracket.what is $a->b mean and have what effect? the sign '->' mean is?

eg:
format_date($comment->timestamp)
anyone's reply is appreciated!

 

$comment is an object and $timestamp is a property of that object. If you do not know this, it's time you buy a book instead of just teaching yourself online.

 

thx
i will do,i know a little.how do you know this is a class not a function?
is see from the sign ->.

 

Because of -> it isn't a function. Read up on the basics. It's a variable in an object instance. If it was a method of that object it would be $comment->method()

 

heres an example of an object

class username(){

    var $username; // this will basically make an empty variable ready for use;

    //we now can create functions within the class object
    function printName(){
        echo $this->username; // now when were inside a function we refer to other vars outside the functions by prepending them with $this->
    }

    function setName($name){
        //this will be run before the above so we can fill that var $username;
        $this->username = $name; //this will fill the username with the name sent to the function
    }
}

$object = new username;

//Now $object basically contains all the functions within the above class file

//so now we can set the name
$object->setName('runeveryday');

//no we have done that the var $username is now = to runeveryday

// now we use the other function to return the username
echo "My name is : " . $object->getName();

PHP:

and there it is

 

thanks!
but the form of
class username(){ }
is right? i know the statement of a class is
class usename{ }.
but in your answer,it's username( ).is it right?