PHP class constructors and methods - php

Question

I just started learning PHP and I am having trouble with its syntax. I am learning how to write a class in php, and I used a syntax kinda similar to Java. However, I can get neither its constructor nor regular method to work and I can't figure out why.
<?php
class bento {
public $food;
public $staple = "rice";
protected $veggie = "kale";
public function __construct($fd){
$food = $fd;
}
public function getstaple(){
return $staple;
}
}
$chicken=new bento("chick");
echo "<br>".$chicken->food;
echo "<br>".$chicken->staple;
$fd=$chicken->getstaple();
echo "<br>".$fd;
echo "<br>".$chicken->getstaple();
?>
Here is the result that I have got:
//result
rice
//end of result
Basically, out of 4 lines, I only got one line to work (print out the $staple variable). The constructor did not assign "chick" value to $food. The getstaple() function did not return any value.
I can't figure out how to get this to work.

Answer 1

To refer to a class member, you should use $this->food or $this->staple
class bento {
public $food;
public $staple = "rice";
protected $veggie = "kale";
public function __construct($fd){
$this->food = $fd;
}
public function getstaple(){
return $this->staple;
}
}

Answer 2

The same in java, you need to access your class variables using the "this" keyword. In php, you would do something like:
$this->methodName();
or
$this->variableName

Answer 3

In PHP all variables are local to the scope they are defined within (with a few language provided exceptions like the superglobals $_GET, $_POST, $REQUEST, $_SERVER etc..)
This means that when you reference $food within your method your are referring to $food as it is defined within that method in other words a function variable as opposed to the instance property that you intended.
For instance methods PHP is nice enough to create for you a reference to the instance that a method was called on called $this This allows for you to reference properties and methods of an object from within the object itself via this format.
$this->food = $fd
Another thing to note is class methods and properties are not accessible this way. They require the use of the scope resolution operator :: so to get at a staticly defined class property or method you would use:
ClassName::method();
or
ClassName::$property;
As with $this php provides some easy access to the class properties via the self and static keywords.
self is a reference to the class that a static method was defined on.
static is a reference to the class that the static method was called on.
To illustrate the difference see this code
class A {
static public $toWho = "Class A";
static public function sayHelloSelf(){
echo "Hello ".self::$toWho;
}
static public function sayHelloStatic(){
eecho "Hello ".static::$toWho;
}
}
class B extends A {
static public $toWho = "Class B";
}
B::sayHelloSelf(); // echos Hello Class A
B::sayHelloStatic(); // echos Hello Class B

Answer 4

this keyword is used to access the class member within the current class.
You create class you have assign some value for variable $food.
then within the function you have tried to access the variable but $food is class variable we cannot access the class members without object or scope resolution operator.
"this" has current object name .