how to warn user if it is used a strange character in eval operation
<pre><code>$op=$_POST['param'];
$statement=eval("return ($op);");
</code></pre>

<p>in 'param', if there is a strange character such letter 'jfsdf' or something else the eval function does not work.  How can I solve this problem?</p>

<p>eval function works only well defined entries such as '54+4*3' on the other hand if it is used entries such '6p+87+4' it gives an parse error. Is there any way to warn user in order to enter a well defined statement</p>
