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In-class access with $this

PHP course · Intermediate · Lesson 4/115

Learn to access the class's properties and methods with the $this pseudo-variable.

What is $this?

$this is a special variable (pseudo-variable) that refers to the current instance inside a method. When a method is called on an instance, $this represents that instance.

To access a property from inside a method you write $this->name. Here -> is the object access operator. The $ sign is used only before $this; it is not written before the property name.

Accessing methods and properties with $this

With $this you can access not only properties but also other methods of the class. A method call is written $this->greet().

Example: in a Greeter class, the greet method reaches the $name property via $this->name and prints a greeting. Without $this, writing just $name makes PHP look for a local variable and miss the property.

Exercise Write the Greeter class with $this

Define a class named Greeter. Add the property public $name = "Guest";. Write a method greet; in the body write echo "Hello, " . $this->name . "!\n";. Do not call the method. After the class, write echo "Greeter ready" . "\n";.

Show example solution 
Inside class Greeter { } add the property, then function greet() { echo ... $this->name ...; }, then echo after the class.
Example solution:
<?php
// Write the Greeter class, the $name property and the greet method
class Greeter {
    public $name = "Guest";
    function greet() {
        echo "Hello, " . $this->name . "!\n";
    }
}
echo "Greeter ready" . "\n";

Test yourself

  1. Which is true about $this?

    • $this represents all instances of a class.
    • $this gives the name of the class.
    • $this refers to the parent class.
    • $this refers to the current instance.
    Show answer

    $this refers to the current instance. — Correct. $this refers to the current instance, giving access to properties and methods.

  2. Complete the property access with $this

    class Greeter {
    public $name = "Guest";
    function greet() {
        echo "Hello, " . ____->name . "!";
    }
}
    Show answer 
    class Greeter {
    public $name = "Guest";
    function greet() {
        echo "Hello, " . $this->name . "!";
    }
}

  3. Match the $this usage

    $this
    Reference to instance
    ->
    Access operator
    $this->name
    Property access
    $this->greet()
    Method call

All lessons in Intermediate

1 Classes

  1. Defining a class
  2. Defining properties
  3. Defining methods
  4. In-class access with $this
  5. Instantiating with new
  6. Summary - Classes

2 Constructor

  1. The __construct method
  2. Passing parameters to the constructor
  3. Initializing properties
  4. Class type declaration
  5. The __destruct method
  6. Summary - Constructor

3 Inheritance

  1. Inheritance with extends
  2. Accessing parent with parent::
  3. Method override
  4. protected property and method
  5. Inheritance chain
  6. Summary - Inheritance

4 Project: Utility library

  1. Project: Utility library
  2. Class skeleton
  3. Adding methods
  4. Using with file inclusion
  5. Project final - Library

5 Visibility

  1. public access
  2. protected access
  3. private access
  4. Encapsulation
  5. Getter and setter methods
  6. Summary - Visibility

6 Static members

  1. static property
  2. static method
  3. In-class access with self::
  4. Late static binding with static::
  5. static vs instance
  6. Summary - Static members

7 Class constants

  1. Class constants with const
  2. Accessing constants
  3. Class name with ::class
  4. Class constants vs static
  5. Constant use cases
  6. Summary - Class constants

8 Project: Quiz app

  1. Project: Quiz app
  2. Designing a question class
  3. Checking answers
  4. Computing the score
  5. Project final - Quiz app

9 Interfaces

  1. Defining interfaces
  2. Implementing with implements
  3. Multiple interfaces
  4. Polymorphism
  5. interface vs abstract
  6. Summary - Interfaces

10 Abstract classes

  1. Defining abstract classes
  2. abstract methods
  3. Abstract class inheritance
  4. Template method pattern
  5. Constructor and abstract
  6. Summary - Abstract classes

11 Traits

  1. Defining traits
  2. Using traits with use
  3. Multiple traits
  4. Resolving method conflicts
  5. Trait vs inheritance
  6. Summary - Traits

12 Project: Blog app

  1. Project: Blog app
  2. Creating a post class
  3. Adding posts with a form
  4. Displaying the post list
  5. Project final - Blog

13 File handling

  1. Reading with file_get_contents()
  2. Writing with file_put_contents()
  3. Opening files with fopen()
  4. fwrite() and fread()
  5. Closing files with fclose()
  6. Summary - File handling

14 File upload

  1. The $_FILES superglobal
  2. move_uploaded_file()
  3. Validating file type
  4. File size limit
  5. Upload error handling
  6. Summary - File upload

15 Sessions

  1. Starting a session with session_start()
  2. Storing data with $_SESSION
  3. Reading from a session
  4. unset() and session_destroy()
  5. Login/logout logic
  6. Summary - Sessions

16 Cookies

  1. Creating cookies with setcookie()
  2. Reading cookies with $_COOKIE
  3. Cookie expiration
  4. Deleting cookies
  5. Session vs cookie
  6. Summary - Cookies

17 Project: Contact form

  1. Project: Contact form
  2. Form skeleton
  3. Validating data
  4. Integrating file upload
  5. Project final - Contact form

18 Error handling

  1. The try/catch block
  2. Throwing exceptions with throw
  3. The Exception class
  4. error_reporting configuration
  5. Custom exception classes
  6. Summary - Error handling

19 Date and time

  1. Formatting dates with date()
  2. Timestamps with time()
  3. Parsing dates with strtotime()
  4. The DateTime class
  5. DateInterval and DatePeriod
  6. Summary - Date and time

20 Intermediate final

  1. Challenge - OOP app
  2. Challenge - File and session
  3. Challenge - Multi-step registration form
  4. Challenge - Error handling
  5. Challenge - Mini API