เกี่ยวกับการตรวจสอบว่ามีการกรอกสัญลักษณ์พิเศษหรือไม่

<?php header ("Content-Type: text/html; charset=tis-620"); ?>
<? 
$userID=$_POST['tUserId'];
$countString=strlen($userID);
$n=1;
$i=1;
if((($userID[0] >="a" && $userID[0] <="z") || ($userID[0] >="0" && $userID[0] <="9" ) || ($userID[0] >="A" && $userID[0] <="Z" )) && (!preg_match("/^([-_!@#$%^&*()=+?])+$/", $userID[0]))){
while($n==1){
if((($userID[$i] >="a" && $userID[$i] <="z") || ($userID[$i] >="0" && $userID[$i] <="9" ) || ($userID[$i] >="A" && $userID[$i] <="Z" )) && (!preg_match("/^([-_!@#$%^&*()=+?])+$/", $userID[$i]))){
if($i=$countString){
echo "<img src='true.PNG'>";
$n=0;
}
$i++;
}else{
echo "<img src='false.PNG'>";
$n=0;
}}
}else{
	echo "<img src='false.PNG'>";
	}
?>