What Does the Variable $This Mean in PHP

What does the variable $this mean in PHP?

It's a reference to the current object, it's most commonly used in object oriented code.

• Reference: http://www.php.net/manual/en/language.oop5.basic.php
• Primer: http://www.phpro.org/tutorials/Object-Oriented-Programming-with-PHP.html

Example:

<?php
class Person {
    public $name;

    function __construct( $name ) {
        $this->name = $name;
    }
};

$jack = new Person('Jack');
echo $jack->name;

This stores the 'Jack' string as a property of the object created.

PHP, $this-{$var} -- what does that mean?

This is a variable variable, such that you will end up with $this->{value-of-$val}.

See: http://php.net/manual/en/language.variables.variable.php

So for example:

$this->a = "hello";
$this->b = "hi";
$this->val = "howdy";

$val = "a";
echo $this->{$val}; // outputs "hello"

$val = "b";
echo $this->{$val}; // outputs "hi"

echo $this->val; // outputs "howdy"

echo $this->{"val"}; // also outputs "howdy"

Working example: http://3v4l.org/QNds9

This of course is working within a class context. You can use variable variables in a local context just as easily like this:

$a = "hello";
$b = "hi";

$val = "a";
echo $$val; // outputs "hello"

$val = "b";
echo $$val; // outputs "hi"

Working example: http://3v4l.org/n16sk

What does 'this followed by square brackets' mean in PHP?

The fact that your variable is called $this means that it can't be an ordinary array - that variable name is reserved for the current instance of a class.

Using square brackets to access an object is a sign that the class implements that ArrayAccess interface - that is, it can be accessed using the operators normally reserved for basic arrays.

Retrieving a value from a class that implements ArrayAccess using square bracket notation invokes the class's offsetGet method, with the provided key as the $offset argument. The most common use is to allow access to a class's member variables, but the class itself can choose to perform any action in this method.

In your case, I think you're looking at the Laravel application class, which will result in the router item being returned from the dependency injection container.

What is the meaning of $this

$this is a reference to the current object.

It can be used in class methods only.

From the manual:

The pseudo-variable $this is available when a method is called from within an object context. $this is a reference to the calling object (usually the object to which the method belongs, but possibly another object, if the method is called statically from the context of a secondary object).

a simple real world example:

class Classname
{
  private $message = "The big brown fox... jumped....";

  function setMessage($givenMessage) {
    $this->message = $givenMessage;
  }

  function getMessage() {
    return $this->message;  // Will output whatever value 
                            // the object's message variable was set to
  }
}

$my_object = new Classname();  // this is a valid object
echo $my_object->getMessage();  // Will output "The big brown fox... jumped...."

$my_object->setMessage("Hello World!");
echo $my_object->getMessage();  // Will output "Hello world"

$this is not available when you call a method in a static context:

Classname::showMessage(); // Will throw an error: 
                          // `$this` used while not in object context

Reference — What does this symbol mean in PHP?

Incrementing / Decrementing Operators

++ increment operator

-- decrement operator

Example    Name              Effect
---------------------------------------------------------------------
++$a       Pre-increment     Increments $a by one, then returns $a.
$a++       Post-increment    Returns $a, then increments $a by one.
--$a       Pre-decrement     Decrements $a by one, then returns $a.
$a--       Post-decrement    Returns $a, then decrements $a by one.

These can go before or after the variable.

If put before the variable, the increment/decrement operation is done to the variable first then the result is returned. If put after the variable, the variable is first returned, then the increment/decrement operation is done.

For example:

$apples = 10;
for ($i = 0; $i < 10; ++$i) {
    echo 'I have ' . $apples-- . " apples. I just ate one.\n";
}

Live example

In the case above ++$i is used, since it is faster. $i++ would have the same results.

Pre-increment is a little bit faster because it really increments the variable and after that 'returns' the result. Post-increment creates a special variable, copies there the value of the first variable and only after the first variable is used, replaces its value with second's.

However, you must use $apples--, since first, you want to display the current number of apples, and then you want to subtract one from it.

You can also increment letters in PHP:

$i = "a";
while ($i < "c") {
    echo $i++;
}

Once z is reached aa is next, and so on.

Note that character variables can be incremented but not decremented and even so only plain ASCII characters (a-z and A-Z) are supported.

---

Stack Overflow Posts:

• Understanding Incrementing

What does $this-{$key} mean in PHP?

Reads the idkey property of the $this object:

$this->idKey;

Reads the variable property name of the $this object (example in this case) so $this->example:

$idKey = 'example';
$this->$idKey;

Same as above ($this->example), but with less ambiguity (similar to adding parentheses to control operand order, and useful in some cases):

$idKey = 'example';
$this->{$idKey};

A case where this may add clarity or control the order:

$this->{$idKey['key']};
$this->{$idKey}['key'];

---

Related Topics