PHP定界符 多行字符串的生成

<code>$符)
(开头无空格)第一行 
<span>XXX</span><span>XXX</span><span>XX</span>(开头无空格)变量(无<span>$符</span>)</code>

<code><span><span><?php </span><span>$s</span> =<span>1
<p>2</p>
<p>3</p>
s;</span><span>echo</span><span>$s</span>;
<span>?></span></span></span></code>

<code>1

2

3</code>

<code><span><?php </span><span>$_data</span> =<span>
<note>
    <to>George</to>
    <from>老三</from>
    <heading>Reminder</heading>
    Don't forget the meeting!
</note>
data;</span><span>$myfile</span> = fopen(<span>"file.txt"</span>, <span>"w"</span>) <span>or</span><span>die</span>(<span>"Unable to open file!"</span>); 
fwrite(<span>$myfile</span>, <span>$_data</span>);
fclose(<span>$myfile</span>);
<span>?></span></span></code>

<code>file.txt内容:
<span><?xml version="1.0" encoding="UTF-8"?></span><span>note</span>><span>to</span>>George<span><span>to</span>></span><span>from</span>>老三<span><span>from</span>></span><span>heading</span>>Reminder<span><span>heading</span>></span><span>body</span>>Don't forget the meeting!<span><span>body</span>></span><span><span>note</span>></span></code>