以前没见过，长见识了

表达字符串的方式

1. 单引号 (一切原样输出)
2. 双引号

3. heredoc 句法结构：<<<
   特别注意的是结束标志不能缩进

    <?php
    $str = <<<EOD
    Example of string
    spanning multiple lines
    using heredoc syntax.
    EOD;
   
    /* 含有变量的更复杂示例 */
    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;
    ?>
   

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

4. nowdoc, 类似heredoc

   参考

   1. http://php.net/manual/zh/language.types.string.php