<?php
header("Content-type: text/html; charset=utf-8"); 
require('conn.php');
$id = intval($_GET['id']);
$sql = "delete from lyb where ID = $id";
if ($mysqli->query($sql) === true) {
    echo "<meta http-equiv='Content-Type'  content='text/html; charset=utf-8'>"; 
    echo "<script charset='utf-8' type='text/javascript'>alert('删除成功');location.href='5-6.php';</script>";
} else {
    echo "删除失败" . $mysqli->error;
    echo  "<script>location.href='5-6.php'</script>";
}
$mysqli->close();
?>

为何删除成功几个字，还是显示为乱码？