Php <<<是什麼意思？

Question

在以下代碼中，http://us2.php.net/manual/en/language.oop5.properties.php符號是什麼意思？

<?php 
class SimpleClass 
{ 
    // invalid property declarations: 
    public $var1 = 'hello ' . 'world'; 
    public $var2 = <<<EOD 
hello world 
EOD; 
    public $var3 = 1+2; 
    public $var4 = self::myStaticMethod(); 
    public $var5 = $myVar; 

    // valid property declarations: 
    public $var6 = myConstant; 
    public $var7 = array(true, false); 

    // This is allowed only in PHP 5.3.0 and later. 
    public $var8 = <<<'EOD' 
hello world 
EOD; 
} 
?> 

Answer 1

它被稱爲Heredoc syntax，可用於分配字符串值。

Answer 2

Heredoc syntax中的字符串。

Answer 3

這只是另一種方式來定義一個String（Newdoc /定界符） - Manual - String