Basically trait is word use in biology. In php trait is method of code re-usability.As we know php is single inheritance programming language.As per my opinion main intention of introducing trait in php is to reduce limitation of code re-usability in PHP single inheritance nature.

PHP VERSION

PHP 5.0
2004 - Abstract classes and interfaces introduced

PHP 5.4
2012 - Traits introduced

Abstract Classes are in reality define things that are abstract e.g Vehicle is an abstract thing until or unless its materialized in the form of a car or a bike . Neither interface define it nor traits.

Interfaces compliment the class inheritance functionality where a class inherits from multiple classes(only certain languages provide multiple inheritance e.g C/C++). Interfaces , as names suggest focus on the INTERFACE , and not the implementation of the interface method in class which is implementing it. It makes classes PULG & PLAYABLE so everyone should follow a standard. If you further read about factory and adapter pattern on OOP you will understand it.

Traits have implementation/functionality that is not bound to specific classes.Instead it could be found across different classes. Its like a gene in genetics which stays mute in parents and appear only in certain children. Or to be concise selective inheritance but not bound to single class. So it provides a way much better code-reuse

Declaration of PHP Trait

  1. trait test_trait
  2. {
  4. public
  5. function traittestFunction()
  6. {
  7. echo "This is callable by your class object";
  8. }
  9. }
Declaring class where traits will be used,
  1. class helloTest
  2. {
  3. use test_trait;
  4. }
  5. $objTest = new helloTest();
  6. $objTest - > traittestFunction();
Output:

This is callable by your class object.