未定义的变量：文件（多行）[重复]

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未定义的变量：文件 - 在多行上

图像部分出现错误，即$ imageName，$ imageType，$ imageSize，$ imageTmp

提交表单时，警报出现“文件类型无效”，错误来了......

php代码在这里 -

<?php
include'includes/connect.php';

if(isset($_POST['submit'])) {
if($_POST['title']=='' or $_POST['content']=='' or $_POST['author']=='') {
    echo('<script>alert("All Fields Are Required")</script>');
    exit;
}else{
    $title = $_POST['title'];
    $author = $_POST['author'];
    $content = $_POST['content'];
    $imageName = $_FILES['image']['name'];
    $imageType = $_FILES['image']['type'];
    $imageSize = $_FILES['image']['size'];
    $imageTmp = $_FILES['image']['tmp_name'];
    $date = date('y.m.d');

    if($imageType=='image/jpeg' or $imageType=='image/jpg' or $imageType=='image/png' or $imageType=='image/gif') {
        if($image_size<=5000000) {
            move_uploaded_file($image_tmp, 'images/image_name');
        }else{
            echo('<script>alert("File size exceeds")</script>');
        }
    }else{
        echo('<script>alert("Invalid file type")</script>');
    }
    $query = "INSERT INTO blog_post ('title','author','image','content','date') VALUES ('$title','$author','$imageName','$content','$date')";
    if(mysqli_query($con,$query)) {
        echo('Inserted');
    }
    /*header("refresh:2; url=blog_post.php");*/
}
}
?>

连接在这里 -

<?php
$con = mysqli_connect("localhost","root","","cms");
?>

请帮忙