织梦dedecms自定义表单添加验证码功能

$fieldarr = explode(';', $wmd_fields);

//新增验证码
if(!empty($wmd_fields))
	{ 
		$validate = empty($validate) ? '' : strtolower(trim($validate));            
		$svali = strtolower(GetCkVdValue());
		if(($validate=='' || $validate != $svali) && preg_match("/6/",$safe_gdopen)){ 
			ResetVdValue(); 
			ShowMsg('验证码不正确!',$wmd_add,0,1000); 
			echo '<script language="javascript">history.go(-1);</script>';
		} 
	}
//end

<input name="validate" type="text" id="vdcode" style="text-transform:uppercase;" size="8"/>
<img id="vdimgck" align="absmiddle" onClick="this.src=this.src+'?'" style="cursor: pointer;" alt="看不清？点击更换" src="../include/vdimgck.php"/>
<a href="javascript:vide(-1);" onClick="changeAuthCode();">看不清？ </a>

<script type="text/javascript" language="javascript">
//验证码
function changeAuthCode() {  
	var num = new Date().getTime();
	var rand = Math.round(Math.random() * 10000); 
	num = num + rand; 
	$('#ver_code').css('visibility','visible'); 
	if ($("#vdimgck")[0]) { 
	    $("#vdimgck")[0].src = "../include/vdimgck.php?tag=" + num; 
	} 
	return false;
}
</script>