用ajax，只有火狐浏览器有显示，其他谷歌不行

<script>
 $(function(){
  $(':input[name=username]').blur(function(){
   $.ajax({
 url:'userExists.php',                                   
 type:'post',                                             
 async:'false',
 data:{'username':$(this).val()},                       
 dataType:'json',                                         
 success:function(data){                                 
  //alert(data[1]);
  if(data[0]==-1){
 $('.abc').css('color','red').html(data[1]);
 }
  else{
 $('.abc').css('color','green').html(data[1]);
 }
   }
 });
});
  });
</script><?php
include('../phpfz5/function.php');
$conn=mysql_connect('localhost','root','123456');
mysql_query('set names utf8');
mysql_select_db('qy_table',$conn);
$username=$_POST['username'];
$sql="select id from users where username='$username'";
$user=find($sql);
 $arr=array();
 if(!empty($user)){
  $arr=array('-1','用户已存在,不可注册');
 }
else{
 $arr=array('0','恭喜！用户可以使用');
 }
 echo json_encode($arr);
?>