PHP上传脚本-文件大小和文件类型问题

我有以下代码用作上传脚本

$allowed_filetypes = array('.jpg', '.jpeg', '.gif', '.bmp', '.png'); 
$max_filesize = 262144; 
$upload_normal_path = '../uploads/normal/'; 
$upload_thumb_path = '../uploads/thumbnail/';
if(isset($_POST['Submit']))
{
$filename = $_FILES['image']['name']; 
$filesize = $_FILES['image']['size']; 
$fileext = substr($filename, strpos($filename,'.'), strlen($filename)-1);
if(!in_array($fileext, $allowed_filetypes)){
$upload_status = "The file you attempted to upload is not allowed.";
}
if($filesize > $max_filesize){
$upload_status = "The file you attempted to upload is too large.";
}
$image_name = time().$fileext;
$newname = $image_name;
$moved = move_uploaded_file($_FILES['image']['tmp_name'],$upload_normal_path . $newname);
if(!$moved){
$upload_status = 'There was an error during the file upload.  Please try again.';
} else {
$upload_status = 'Your file upload was successful, view the file <a href="' . $upload_normal_path . $newname . '" title="Your File">here</a>';
}
}

脚本本身有时似乎有效，但它似乎跳过了一些情境IF和ELSE。例如，如果文件大小大于$filesize，我没有得到正确的$upload_status，应该说"你试图上传的文件太大"，相反，它似乎一直跳到"文件上传过程中出错。请重试"。此外，有时我可以通过上传一些MP3或HTML文件，这意味着它会跳过整个（！in_array（$fileext，$allowed_filetypes））。

任何可能导致这些问题的原因以及如何解决的想法。致以最诚挚的问候

[已解决]感谢大家的时间和回答，非常感谢。在看了你的答案后，我做了一些代码清理，直到我让它做我需要它做的事情。

因此，这里是我当前代码的副本，希望它能帮助任何可能遇到此类问题的开发人员。

致以最诚挚的问候

当前工作代码：

function make_thumb($img_name,$filename,$new_w,$new_h)
{
$ext=getExtension($img_name);
if(!strcmp("jpg",$ext) || !strcmp("jpeg",$ext))
$src_img=imagecreatefromjpeg($img_name);
if(!strcmp("png",$ext))
$src_img=imagecreatefrompng($img_name);

$old_x=imageSX($src_img);
$old_y=imageSY($src_img);
$ratio1=$old_x/$new_w;
$ratio2=$old_y/$new_h;
if($ratio1>$ratio2) {
$thumb_w=$new_w;
$thumb_h=$old_y/$ratio1;
}
else {
$thumb_h=$new_h;
$thumb_w=$old_x/$ratio2;
}
$dst_img=ImageCreateTrueColor($thumb_w,$thumb_h);
imagecopyresampled($dst_img,$src_img,0,0,0,0,$thumb_w,$thumb_h,$old_x,$old_y);
if(!strcmp("png",$ext))
imagepng($dst_img,$filename);
else
imagejpeg($dst_img,$filename);
imagedestroy($dst_img);
imagedestroy($src_img);
}
function getExtension($str) {
$i = strrpos($str,".");
if (!$i) { return ""; }
$l = strlen($str) - $i;
$ext = substr($str,$i+1,$l);
return $ext;
}
$upload_status = "";
$max_filesize = 2097152;
$error = 0;
$allowed_filetypes = array('jpg', 'jpeg', 'png', 'JPG', 'JPEG', 'PNG'); 
if(isset($_POST['Submit']))
{
$image = $_FILES['image']['name'];
if ($image)
{
$filename = stripslashes($_FILES['image']['name']);
$sizekb = filesize($_FILES['image']['tmp_name']);
$extension = getExtension($filename);
$extension = strtolower($extension);
    if(!in_array($extension, $allowed_filetypes)){
    $upload_status = "<div id='file-upload'><div class='upload-bar-error'><span class='upload-error'>The file extension is not supported.</span></div></div>";
    $error = 1;
    }
    if(isset($_SERVER['CONTENT_LENGTH']) && $_SERVER['CONTENT_LENGTH']> $max_filesize){
    $upload_status = "<div id='file-upload'><div class='upload-bar-error'><span class='upload-error'>The file size has extended the size limit.</span></div></div>";
    $error = 1;
    }
    if($error == 0){
    $image_name=time().'.'.$extension;
    $newname="../uploads/normal/".$image_name;
    $newname_db = "uploads/normal/".$image_name;
    copy($_FILES['image']['tmp_name'], $newname);
    $thumb_name='../uploads/thumbnail/thumb_'.$image_name;
    $thumb_name_db = 'uploads/thumbnail/thumb_'.$image_name;
    $thumb = make_thumb($newname,$thumb_name,$thumb_width,$thumb_height);
    $upload_status = "<div id='file-upload'><div class='upload-bar-success'><span class='upload-success'>The file has been uploaded successfully.</span></div></div>";
    }
}
}