Why do I get this error "Fatal error: Cannot access empty property in"

[pahunrepublic]

I'm just self-learning OOP PHP and I have this sample code and I get this error

Fatal error: Cannot access empty property in Rectangle.php on line 25

:

Rectangle.php

<?php # Script 6.3 - Rectangle.php
/* This page defines the Rectangle
class. The class contains two attributes:
width and height.
The class contains four methods:
- set_size()
- get_area()
- get_perimeter()
- is_square()
*/
class Rectangle {
//Declare attributes.
public $width = 0;
public $height = 0;
//Method to set the dimensions.
function set_size($w= 0, $h = 0) {
$this->$width = $w;
$this->$height = $h;
}
//Method to calculate and return the area
function get_area(){
return ($this->width * $this-height);
}
//Method to calculate and return the perimeter.
function get_perimeter() {
return (($this->width + $this->height) * 2);
}
//final method that indicates if the rectangle is also a square
function is_square() {
if ($this->width == $this->height) {
	return true;
} else {
	return false;
}
}
}//end of Rectangle class
?>

and rectangle1.php

<?php 
require_once('Rectangle.php');
$width = 42;
$height = 7;
// Print a little introduction:
echo "<h3>With a width of $width and a height of $height...</h3>";

// Create a new object:
$r = new Rectangle();
// Assign the rectangle dimensions.
$r->set_size($width, $height);
// Print the area.
echo '<p>The area of the rectangle is ' . $r->get_area() . '</p>';
// Print the perimeter.
echo '<p>The perimeter of the rectangle is ' . $r->get_perimeter() . '</p>';
// Is this a square?
echo '<p>This rectangle is';
if ($r->is_square()) {
echo 'also';
} else {
echo 'not';
}
echo 'a square.</p>';
// Delete the object:
unset($r);
?>

Any idea why do I get this error. I can't trace the bug because as I said I'm beginner in OOP PHP. Please help

[xyph]

Here's a problem

 

function set_size($w= 0, $h = 0) {
   $this->$width = $w;
   $this->$height = $h;
   }

 

You want

 

function set_size($w= 0, $h = 0) {
   $this->width = $w;
   $this->height = $h;
   }

 

 

Also

function get_area(){
return ($this->width * $this-height);
}

 

 

Should be

 

 

function get_area(){
return ($this->width * $this->height);
}

 

 

Pay attention to both the file the error is in, and the line. It should help you isolate your issue

[fugix]

if the syntax errors that xyph pointed out do not solve you issue, please post the exactl line that the error is occurring on

[wildteen88]

You're not setting the width and height properties within the set_size method correctly

function set_size($w= 0, $h = 0) {
$this->$width = $w;
$this->$height = $h;
}

You should be using $this->width and $this->height not $this->$width and $this->$height

 

Another issue you have is on this line

return ($this->width * $this-height);

You have left of the > after $this-

[fugix]

You're not setting the width and height properties within the set_size method correctly

function set_size($w= 0, $h = 0) {
$this->$width = $w;
$this->$height = $h;
}

You should be using $this->width and $this->height not $this->$width and $this->$height

 

Another issue you have is on this line

return ($this->width * $this-height);

You have left of the > after $this-

xyph pointed these exact issues out wildteen...

[wildteen88]

xyph pointed these exact issues out wildteen...

Oh.. I didn't realise xyph had replied. Must of posted as I was typing my reply.

[fugix]

xyph pointed these exact issues out wildteen...

Oh.. I didn't realise xyph had replied. Must of posted as I was typing my reply.

no worries, happens to me all of the time..heh

[pahunrepublic]

Thank You all xiyph, fugix. It seems the problems were all typo related. Wow I didn't copy well the script from the book.