请大神赐教！

最近正在学习php 用elseif做了一个后端程序验证注册表单，验证程序卡在 密码是否为空的验证那一步，不往下走了，只要用户名符合要求，就一直提示密码不能为空。
这是表单页面：
<h1>后端程序验证注册表单（elseif）</h1>
<div class="div1">
<?php
$str = "1234567890qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";
$code = "<span style='color:rgb(" . mt_rand(0,255) . "," . mt_rand(0,255) . "," . mt_rand(0,255) . ")'>" . $str{mt_rand(0, strlen($str)-1)} . "</span>";
$code .= "<span style='color:rgb(" . mt_rand(0,255) . "," . mt_rand(0,255) . "," . mt_rand(0,255) . ")'>" . $str{mt_rand(0, strlen($str)-1)} . "</span>";
$code .= "<span style='color:rgb(" . mt_rand(0,255) . "," . mt_rand(0,255) . "," . mt_rand(0,255) . ")'>" . $str{mt_rand(0, strlen($str)-1)} . "</span>";
$code .= "<span style='color:rgb(" . mt_rand(0,255) . "," . mt_rand(0,255) . "," . mt_rand(0,255) . ")'>" . $str{mt_rand(0, strlen($str)-1)} . "</span>";
$code .= "<span style='color:rgb(" . mt_rand(0,255) . "," . mt_rand(0,255) . "," . mt_rand(0,255) . ")'>" . $str{mt_rand(0, strlen($str)-1)} . "</span>";
?>
<form action="doAction2.php" method="post">
<table border="1" width="800" align="center">
<tr>
<td align="right">用户名</td>
<td><input type="text" name="username" placeholder="请输入用户名"/>
用户名长度为5~10之间，且以小写字母开头
</td>
</tr>
<tr>
<td align="right">密码</td>
<td><input type="password" name="password"/>
密码不能为空
</td>
</tr>
<tr>
<td align="right">确认密码</td>
<td><input type="password" name="repassword"/>
两次密码一致
</td>
</tr>
<tr>
<td align="right">邮箱</td>
<td><input type="text" name="email"/>
请输入正确的邮箱地址
</td>
</tr>
<tr>
<td align="right">验证码</td>
<td>
<input type="text" name="verify" placeholder="请输入验证码"/> <?php echo $code ?>
<input type="hidden" name="verify1" value="<?php echo strip_tags($code) ?>"/>
</td>
</tr>
<tr>
<td colspan="2" align="center"><input type="submit" value="注册"/></td>
</tr>
</table>
</form>
</div>
<p>
</body>
这是doAction2页面：
<?php
//接收数据
//$_POST:表单以POST方式发送数据，就用$_POST来接收数据
$username = $_POST['username'];
$password = $REQUEST['password'];
$repassword = $REQUEST['repassword'];
$email = $REQUEST['email'];
$verify = strtolower($REQUEST['verify']);
$verify1 = strtolower($REQUEST['verify1']);
// 验证用户名
$userLen = strlen($username);
$ascii = ord($username{0});
$pwLen = strlen($password);
if ($userLen < 5 || $userLen > 10) {
$mes = "用户名长度不符合规范";
}elseif ($ascii < 97 || $ascii > 122) {
$mes = "用户名必须以小写字母开头";
}elseif ($pwLen == 0) {
$mes = "密码不能为空";
}elseif ($password != $repassword){
$mes = "两次密码不一致";
}elseif (strpos($email, "@") == false){
$mes = "邮箱不符合规范";
}elseif ($verify != $verify1) {
$mes = "验证码不正确";
}else{
$mes = "表单验证成功！";
}
echo $mes;
?>