PHP trait_exists() Function

PHP implements a way to reuse code called Traits. The trait_exists() function in PHP is an inbuilt function that is used to check whether a trait exists or not. This function accepts the traitname and autoload as parameters and returns true if trait exists, false if not, null in case of an error.

Syntax :

trait_exists ( string $traitname , bool $autoload = ? ) : bool

Parameters: This function accepts two parameters as mentioned above and described below.

• $traitname: This parameter contains the name of the trait.
• $autoload: This parameter is a boolean value that tells whether to autoload, if not already loaded.

Return Value:

• It returns true, if a trait exists.
• It returns false, if the trait does not exist.
• It returns null for any error encountered.

Example 1:

PHP

<?php

// Created trait Programming
trait Programming
{
    // Declared static instance
    private static $instance;
    protected $temp;

   // Defining static function in trait to Reuse
    public static function Designing()
    {
        self::$instance = new static();
        // Magic constant __TRAIT__ in PHP
        // It gets the class name for the static method called.
        self::$instance->temp = get_called_class().' '.__TRAIT__;

        return self::$instance;
    }

}
// Checking if 'Programming' Trait exists
if ( trait_exists( 'Programming' ) )
{

    class Initializing
    {
        // Reusing trait 'Programming'
        use Programming;

        public function text( $strParam )
        {
            return $this->temp.$strParam;
        }
    }

}

echo Initializing::Designing()->text('!!!');

?>

Output:

Initializing Programming!!!

Example 2: 

PHP

<?php

// Creating Base class
class Base
{
    public function callBase()
     {
        echo 'This is base function!'."<br>";
     }
}

// Creating Trait
trait myTrait {
    public function callBase()
    {
        parent::callBase();
         echo 'This is trait function!'."<br>";
    }
}

// Using myTrait
class myClass extends Base
{
    use myTrait;
}

$myObject = new myClass();
$myObject->callBase();

// Checking if trait exists
if(trait_exists( "myTrait"))
{
    echo "\n myTrait exists! \n";
}
else
{
  echo "\n myTrait does not exists! \n";

}

?>

Output:

This is base function!
This is trait function!
myTrait exists!

Reference : https://www.php.net/manual/en/function.trait-exists.php