Heredoc和Nowdoc

就象heredoc结构类似于双引号字符串，Nowdoc结构是类似于单引号字符串的。Nowdoc结构很象heredoc结构，但是 nowdoc不进行解析操作 。 这种结构很适合用在不需要进行转义的PHP代码和其它大段文本。与SGML的 <![CDATA[ ]]> 结构是用来声明大段的不用解析的文本类似，nowdoc结构也有相同的特征。

一个nowdoc结构也用和heredocs结构一样的标记 <<<， 但是跟在后面的标志符要用单引号括起来，就像<<<'EOT'这样。heredocs结构的所有规则也同样适用于nowdoc结构，尤其是结束标志符的规则。

Example #2 Heredoc结构的字符串示例

<?php
$str = <<<EOD
Example of string //注释也会被输出
spanning multiple lines
using heredoc syntax.
EOD;

class foo
{
    var $foo;
    var $bar;

    function foo()
    {
        $this->foo = 'Foo';
        $this->bar = array('Bar1', 'Bar2', 'Bar3');
    }
}

$foo = new foo();
$name = 'MyName';

echo <<<EOT
My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should print a capital 'A': x41
EOT;
?>

以上例程会输出：

My name is "MyName". I am printing some Foo.
Now, I am printing some Bar2.
This should print a capital 'A': A

Example #6 Nowdoc结构字符串示例

<?php
$str = <<<'EOD'
Example of string
spanning multiple lines
using nowdoc syntax.
EOD;

class foo
{
    public $foo;
    public $bar;

    function foo()
    {
        $this->foo = 'Foo';
        $this->bar = array('Bar1', 'Bar2', 'Bar3');
    }
}

$foo = new foo();
$name = 'MyName';

echo <<<'EOT'
My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should not print a capital 'A': x41
EOT;
?>
以上例程会输出：

My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should not print a capital 'A': x41