Help Using Classes

I am having some trouble learning how to use classes. I've tried looking up stuff online, read in books, and I can't figure out why this doesn't work.

Here is the class:

class artist{
	//variables
	var $name;
	var $num_of_fans;
	var $link;
	var $desc;
	var $image;
	
	//constructor
	function artist($name) {
		global $cxn;
		global $t_artist;
		$query = "SELECT * FROM $t_artist WHERE name = \"$name\"";
		$result = mysqli_query($cxn,$query);
		
		$row = mysqli_fetch_assoc($result);
		$this->$name = $row['name'];
		$this->$num_of_fans = $row['num_of_fans'];
		$this->$link = $row['link'];
		$this->$desc = $row['description'];
		$this->$image = $row['image']; 
		return;
	}
	
	function sayHi(){
		echo "Hello!";
		return;	
	}
}

PHP:

And here is where I construct it. I tried adding echo statements to the constructor, and they all came out fine, so I'm assuming that there is a problem with this part here:

<?php
$the_band = new artist("Metallica");

//these two lines don't do anything
$the_band->sayHi();
echo $the_band->name;

?>

PHP:

Can someone help me out here?

 

Try

class artist{
    //variables
    var $name;
    var $num_of_fans;
    var $link;
    var $desc;
    var $image;
   
    //constructor
    function artist($name) {
        global $cxn;
        global $t_artist;
        $query = "SELECT * FROM $t_artist WHERE name = \"$name\"";
        $result = mysqli_query($cxn,$query);

        $row = mysqli_fetch_assoc($result);
         $this->name = $row['name'];
        $this->num_of_fans = $row['num_of_fans'];
        $this->link = $row['link'];
        $this->desc = $row['description'];
        $this->image = $row['image']; 
    }
   
    function sayHi(){
        $e = echo "Hello!";
        return $e;
    }
}

PHP:

 

Try this code and see if it's work.

class artist{
    //variables
    var $name;
    var $num_of_fans;
    var $link;
    var $desc;
    var $image;
   
    //constructor
    function artist($name) {
              
        $mysqli = new mysqli ("yourserver", "username", "password", "yourdatabase"); //<----change this line to your setting

        $result = $mysqli->query("SELECT * FROM $t_artist WHERE name = \"$name\"");
        $row = $result->fetch_array(MYSQLI_ASSOC);
        
        $this->name = $row['name'];
        $this->num_of_fans = $row['num_of_fans'];
        $this->link = $row['link'];
        $this->desc = $row['description'];
        $this->image = $row['image'];
      
        $mysqli->close();

        return;
        
    }//end constructor
   
    function sayHi(){
        echo "Hello!";
        return; 
    }
}//end class


$the_band = new artist("Metallica");

//these two lines don't do anything
$the_band->sayHi();
echo $the_band->name;

PHP:

 

This should fix the problem. Just to elaborate, $this->name references a property of the object. $this->$name references a property of the object which $name evaluates to. $name is a variable.

You could do this:

$name = 'link';

Now these two are equal:

$this->$name;
$this->link;