PHP OOP Traits

PHP – What are Traits?

PHP only supports single inheritance: a child class can inherit only from one single parent.

So, what if a class needs to inherit multiple behaviors? OOP traits solve this problem.

Traits are used to declare methods that can be used in multiple classes. Traits can have methods and abstract methods that can be used in multiple classes, and the methods can have any access modifier (public, private, or protected).

Traits are declared with the trait keyword:

Syntax

<?php
trait TraitName {
  // some code…
}
?>

To use a trait in a class, use the use keyword:

Syntax

<?php
class MyClass {
  use TraitName;
}
?>

Let’s look at an example:

Example

<?php
trait message1 {
public function msg1() {
    echo "OOP is fun! ";
  }
}

class Welcome {
  use message1;
}

$obj = new Welcome();
$obj->msg1();
?>

Example Explained

Here, we declare one trait: message1. Then, we create a class: Welcome. The class uses the trait, and all the methods in the trait will be available in the class.

If other classes need to use the msg1() function, simply use the message1 trait in those classes. This reduces code duplication, because there is no need to redeclare the same method over and over again.

PHP – Using Multiple Traits

Let’s look at another example:

Example

<?php
trait message1 {
  public function msg1() {
    echo "OOP is fun! ";
  }
}

trait message2 {
  public function msg2() {
    echo "OOP reduces code duplication!";
  }
}

class Welcome {
  use message1;
}

class Welcome2 {
  use message1, message2;
}

$obj = new Welcome();
$obj->msg1();
echo "<br>";

$obj2 = new Welcome2();
$obj2->msg1();
$obj2->msg2();
?>

Example Explained

Here, we declare two traits: message1 and message2. Then, we create two classes: Welcome and Welcome2. The first class (Welcome) uses the message1 trait, and the second class (Welcome2) uses both message1 and message2 traits (multiple traits are separated by comma).