trait_exists

(PHP 5 >= 5.4.0, PHP 7, PHP 8)

trait_exists — 检查指定的 trait 是否存在

说明

trait_exists(string $trait, bool $autoload = true): bool

参数

trait: 待检查的 trait 的名称
autoload: 如果尚未加载，是否使用自动加载（autoload）。

返回值

如果 trait 存在返回 true，否则返回 false。

add a note

User Contributed Notes 3 notes

down

Lubaev.K ¶

9 years ago


<?php
trait World {

    private static $instance;
    protected $tmp;

    public static function World()
    {
        self::$instance = new static();
        self::$instance->tmp = get_called_class().' '.__TRAIT__;
        
        return self::$instance;
    }

}

if ( trait_exists( 'World' ) ) {
    
    class Hello {
        use World;

        public function text( $str )
        {
            return $this->tmp.$str;
        }
    }

}

echo Hello::World()->text('!!!'); // Hello World!!!

down

astinus dot eberhard at gmail dot com ¶

5 years ago


Traits are compatible with class autoload mechanism - in fact, if you look at source code of trait_exists function, you will find similar peace of code (see Zend/zend_builtin_functions.c)

down

valerio dot bozzolan at gmail dot com ¶

6 years ago


What is the default value of $autoload? And in which way traits are autoloaded? Is there something as spl_autoload() for traits?

add a note