oop - When would you use the $this keyword in PHP?

Question

When would you use the $this keyword in PHP? From what I understand $this refers to the object created without knowing the objects name.

Also the keyword $this can only be used within a method?

An example would be great to show when you can use $this.

Answer 1

A class may contain its own constants, variables (called "properties"), and functions (called "methods").

<?php
class SimpleClass
{
    // property declaration
    public $var = 'a default value';

    // method declaration
    public function displayVar() {
        echo $this->var;
    }
}
?>

Some examples of the $this pseudo-variable:

<?php
class A
{
    function foo()
    {
        if (isset($this)) {
            echo '$this is defined (';
            echo get_class($this);
            echo ")
";
        } else {
            echo "$this is not defined.
";
        }
    }
}

class B
{
    function bar()
    {
        // Note: the next line will issue a warning if E_STRICT is enabled.
        A::foo();
    }
}

$a = new A();
$a->foo();

// Note: the next line will issue a warning if E_STRICT is enabled.
A::foo();
$b = new B();
$b->bar();

// Note: the next line will issue a warning if E_STRICT is enabled.
B::bar();
?>

The above example will output:

• $this is defined (A)
• $this is not defined.
• $this is defined (B)
• $this is not defined.