Fatal error: Cannot use isset() on the result of an expression
<p>When coding with <code>isset</code> i am getting an fatal error.I have searched stackoverflow but results are not satisfactory.</p>

<p>I am getting </p>

<blockquote>
  <p>Fatal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead)</p>
</blockquote>

<p><strong>My codes are</strong></p>

<pre><code>if (!isset( $size || $color )) {
    $style = '';    
}else{
    $style = 'font-size : ' . $size . ';color:' . $color;   
}
</code></pre>