我是php的初学者，我想知道是否有可能在不使用jQuery的情况下进行用户名可用性检查，我的意思是纯php / html？我尝试使用$ _POST [＆＃39;用户名＆＃39;] = $用户名或使用$ _SESSION [＆＃39;用户名＆＃39;] = $用户名然后$ _POST [＆＃39;用户名＆＃ 39;] = $ _ SESSION [＆＃39;用户名＆＃39;]保持用户名输入框中的用户名不被删除（在点击“检查用户名”按钮后）并且失败。我知道这对我来说可能听起来很愚蠢，但也许还有另外一种方式吗？这是第一个代码：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>New Member</title>
</head>
<body>
<center>
<h3>@------------ Create New Account ------------@</h3>
<form method="post" name="form1">
<table width="299" border="0">
<tbody>
<tr>
<td width="62">Username</td>
<center><td>:<br></td></center>
<td colspan="2"><input type="text" name="username">
<input type="submit" name="check" value="Check">
<?php
include('connection.php');
if(isset($_POST['check']))
{
$userchk=$_POST['username'];
$query="select username from login where username='$userchk'";
$check=mysqli_query($connection,$query);
if(mysqli_num_rows($check)==1)
{
echo "Username already in used";
}
else
{
$_POST['username']=$userchk;
echo "Username available";
}
}
?></td>
</tr>
</tbody>
</table>
</form>
<form method="post" name="form2" action="signup_process.php">
<table>
<tbody>
<tr>
<td height="66">Email</td>
<center><td>:</td></center>
<td colspan="2"><input type="text" name="email"></td>
</tr>
<tr>
<td height="74">Sites</td>
<center><td>:</td></center>
<td colspan="2"><input type="text" name="sites"></td>
</tr>
<tr>
<td>Password</td>
<center><td>:</td></center>
<td colspan="2"><input type="text" name="password"></td>
</tr>
<tr>
<td></td>
<center>
<td width="6"> </td>
<td width="72"><input type="submit" name="submit" value="Submit"></td>
<td width="115"><input type="reset" name="reset" value="Reset"></td>
<td width="22"> </td>
</center>
</tr>
</tbody>
</table>
</form>
</center>
</body>
</html>
第二个代码：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>New Member</title>
</head>
<body>
<center>
<h3>@------------ Create New Account ------------@</h3>
<form method="post" name="form1">
<table width="299" border="0">
<tbody>
<tr>
<td width="62">Username</td>
<center><td>:<br></td></center>
<td colspan="2"><input type="text" name="username">
<input type="submit" name="check" value="Check">
<?php
include('connection.php');
if(isset($_POST['check']))
{
$userchk=$_POST['username'];
$query="select username from login where username='$userchk'";
$check=mysqli_query($connection,$query);
if(mysqli_num_rows($check)==1)
{
echo "Username already in used.";
}
else
{
session_start();
$_SESSION['username']=$userchk;
$_POST['username']=$_SESSION['username'];
echo "Username available.";
}
}
?></td>
</tr>
</tbody>
</table>
</form>
<form method="post" name="form2" action="signup_process.php">
<table>
<tbody>
<tr>
<td height="66">Email</td>
<center><td>:</td></center>
<td colspan="2"><input type="text" name="email"></td>
</tr>
<tr>
<td height="74">Sites</td>
<center><td>:</td></center>
<td colspan="2"><input type="text" name="sites"></td>
</tr>
<tr>
<td>Password</td>
<center><td>:</td></center>
<td colspan="2"><input type="text" name="password"></td>
</tr>
<tr>
<td></td>
<center>
<td width="6"> </td>
<td width="72"><input type="submit" name="submit" value="Submit"></td>
<td width="115"><input type="reset" name="reset" value="Reset"></td>
<td width="22"> </td>
</center>
</tr>
</tbody>
</table>
</form>
</center>
</body>
</html>
谢谢。