What is wrong with this PHP code - Unexpected T_CONSTANT
<p>I keep getting the following error in my log</p>

<pre><code>PHP Parse error:  syntax error, unexpected T_CONSTANT_ENCAPSED_STRING, expecting ',' or ';'
</code></pre>

<p>The error is related to this line but I'm not sure what's wrong with it</p>

<pre><code>&lt;?php 
if ($num != null) {
    $query_string = 'msisdn=' . $num . '&amp;ref=' . get_post_meta($post-&gt;ID, "ref", $single = true) ;
    echo '&lt;div class="highlight"&gt;&lt;a href="http://www.site.com/exJoin?signup=y&amp;' .     htmlentities($query_string) . '"&gt;&lt;b&gt;Join Now&lt;/b&gt;&lt;/a&gt;&lt;/div&gt;';
}
else{
    echo '&lt;div class="highlight"&gt;&lt;a href="&lt;?php echo TeraWurflHelper::getPhoneHref('+2711111111'); ?&gt;"&gt;&lt;b&gt;Join Now&lt;/b&gt;&lt;/a&gt;&lt;/div&gt;';
}
?&gt;
</code></pre>
