showing error message in php
<p>want to show a error message as a result of a form action. For example </p>

<pre><code>&lt;form action=a.php
      input .....
&lt;/form&gt;
&lt;span.....&gt;
&lt;?php 
    $variable(Initially the value of this variable null according to the result of form value will change)
?&gt;
&lt;/span&gt;
</code></pre>

<p>For a specific condition I want to set a value of $variable in a.php page and  return to form page using <code>header();</code> . But <code>$variable</code> does not change. How can I change $variable from a.php ?</p>
