Parse error: syntax error, unexpected T_CONSTANT_ENCAPSED_STRING, expecting ']'

Here is the code:

It's making me blind. Can someone help me please? I see one single quote. But I don't know where to add the other one.

<li class="<?php echo ($_SESSION[" m="" ]="=" 'home="" ?="" active="" :="" )="">"&gt; <a href="index.php">Home</a></li>
<li class="<?php echo ($_SESSION[" m="" ]="=" 'bio="" ?="" current="" :="" )="">"&gt; <a href="bio.php">Bio</a> </li>
<li class="<?php echo ($_SESSION[" m="" ]="=" 'appointment="" ?="" current="" :="" )="">"&gt; <a...

Parse error: syntax error, unexpected T_CONSTANT_ENCAPSED_STRING, expecting ']'