检查用户名是否已在mysql中存在的php写法

PHP 2018-12-30

在写注册系统时，如果要检查用户名是否存在，PHP可以这样写：
<div class="codetitle"><a style="CURSOR: pointer" data="58782" class="copybut" id="copybut58782" onclick="doCopy('code58782')"> 代码如下:

<div class="codebody" id="code58782">
$username=$_REQUEST['username'];
$password=$_REQUEST['password'];
echo "
excute the insertUserInfo";
$con=MysqLi_connect("localhost","root","","my_db");
$sql="SELECT * FROM user WHERE username='$username'"; ho "
this username aready exists"; } else { $sql="INSERT INTO user (username,password) VALUES ('$username','$password')"; if(!MysqLi_query($con,$sql)) { echo "
Error".MysqLi_error($con); } else { echo "
one record added"; } }

建议不要用：
<div class="codetitle"><a style="CURSOR: pointer" data="50496" class="copybut" id="copybut50496" onclick="doCopy('code50496')"> 代码如下:

<div class="codebody" id="code50496">
MysqL_num_rows($result)
lt;pre name="code" class="html">

mysql

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