この課題文のどこが間違っているのか教えてください。

この課題文のどこが間違っていますか?

$mailbody=<<<mailbody<br />
<table width='100%' border='1' cellspacing='0' cellpadding='0'>  <br />
		<tr>    <td>Product NO. </td>    <td>"$_POST['productnumber']"</td>  </tr>  <br />
		<tr>    <td>Name</td>    <td>"$_POST['username']"</td>  </tr>  <br />
		<tr>    <td>Promotion code </td>    <td>"$_POST['promotion']"</td>  </tr>  <br />
		<tr>    <td>Mobilephone</td>    <td>"$_POST['mobilephone']"</td>  </tr>  <br />
		<tr>    <td>Age</td>    <td>"$_POST['age']"</td>  </tr>  <br />
		<tr>    <td>Sex</td>    <td>"$_POST['sex']"</td>  </tr>  <br />
		<tr>    <td>Address</td>    <td>}"$_POST['address']"</td>  </tr>  <br />
		<tr>    <td>Prescription Type </td>    <td>"$_POST['prescription']"</td>  </tr>  <br />
		<tr>    <td>Single PD </td>    <td>"$singlepd"</td>  </tr>  <br />
		<tr>    <td>Right PD </td>    <td>"$rightpd"</td>  </tr>  <br />
		<tr>    <td>Left PD </td>    <td>"$leftpd"</td>  </tr>  <br />
		<tr>    <td>Right OD SPH </td>    <td>"$_POST['odsph']"</td>  </tr>  <br />
		<tr>    <td>Left OS SPH </td>    <td>"$_POST['ossph']"</td>  </tr>  <br />
		<tr>    <td>OD CYL </td>    <td>"$_POST['odcyl']"</td>  </tr>  <br />
		<tr>    <td>OS CYL </td>    <td>"$_POST['oscyl']"</td>  </tr>  <br />
		<tr>    <td>OD AXIS </td>    <td>"$_POST['odaxis']"</td>  </tr>  <br />
		<tr>    <td>OS AXIS </td>    <td>"$_POST['oxaxis']"</td>  </tr><br />
</table><br />
mailbody;<br />
echo mailbody;<br />

-----解決策--------------------------
このように「 $_POST['productnumber'] 」を {$_POST['productnumber']} に変更します