trait_exists

(PHP 5 >= 5.4.0, PHP 7)

trait_exists检查指定的 trait 是否存在

说明

bool trait_exists ( string $traitname [, bool $autoload ] )

参数

traitname

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,不存在则返回 FALSE。发生错误的时候返回 NULL

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User Contributed Notes 3 notes

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12
Lubaev.K
4 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!!!
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3
astinus dot eberhard at gmail dot com
1 year 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)
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4
valerio dot bozzolan at gmail dot com
2 years ago
What is the default value of $autoload? And in which way traits are autoloaded? Is there something as spl_autoload() for traits?
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