小编Den*_*ler的帖子

我的php代码收到错误,如下所示:

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home4/iamden83/public_html/loop/signup.php:1) in /home4/iamden83/public_html/loop/signup.php on line 2

代码是这样的

<?php
session_start();
// If user is logged in, header them away
if( isset( $_SESSION["username"] ) ){
    header( "location: message.php?msg=NO to that weenis" );
    exit();
}
?><?php
// Ajax calls this NAME CHECK code to execute
if(isset($_POST["usernamecheck"])){
    include_once("php_includes/db_conx.php");
    $username = preg_replace('#[^a-z0-9]#i', '', $_POST['usernamecheck']);
    $sql = "SELECT id FROM users WHERE username='$username' LIMIT 1";
    $query = mysqli_query($db_conx, $sql); 
    $uname_check …