存储上传的图像文件时遇到问题

我有两个文件希望用户上传。表单如下所示。

<form action="send-image.php" method="POST" enctype="multipart/form-data">
  Upload image 1
        <input type="file" name="FrontDesign">
  Upload image 2
        <input type="file" name="BackDesign">
        <input type="submit" value="Submit images" >
</form>

它发送信息的 PHP 文件如下所示：

require 'includes/PHPMailer/PHPMailerAutoload.php';
$frontdesign = $_FILES['FrontDesign'];
$backdesign = $_FILES['BackDesign'];
$target_path = "";
$target_path2 = "";
if(isset($_POST['FrontDesign'])) {
if (($_FILES["FrontDesign"]["size"] < 1200000000000)){
    if($_FILES["FrontDesign"]["type"] == "image/jpeg"){$ptype=".jpeg";}
    elseif($_FILES["FrontDesign"]["type"] == "image/jpg"){$ptype=".jpg";}
    elseif($_FILES["FrontDesign"]["type"] == "image/pjpeg"){$ptype=".pjpeg";}
    elseif($_FILES["FrontDesign"]["type"] == "image/png"){$ptype=".png";}
    $target_path = "Images/";
    $randf = rand(1000, 9999).rand(1000, 9999).rand(1000, 9999).rand(1000, 9999).rand(1000, 9999);
    $target_path = $target_path . $randf . $ptype; 
    move_uploaded_file($_FILES['FrontDesign']['tmp_name'], $target_path);
    // wrong file type
    } else{echo  $error =1; }
} else { $target_path = 0; }
if(isset($_POST['BackDesign'])) {
    if (($_FILES["BackDesign"]["size"] < 1200000000000)){
        if($_FILES["BackDesign"]["type"] == "image/jpeg"){$ptype2=".jpeg";}
        elseif($_FILES["BackDesign"]["type"] == "image/jpg"){$ptype2=".jpg";}
        elseif($_FILES["BackDesign"]["type"] == "image/pjpeg"){$ptype2=".pjpeg";}
        elseif($_FILES["BackDesign"]["type"] == "image/png"){$ptype2=".png";}
        $target_path2 = "Images/";
        $randf2= rand(1000, 9999).rand(1000, 9999).rand(1000, 9999).rand(1000, 9999).rand(1000, 9999);
        $target_path2 = $target_path2 . $randf2 . $ptype2; 
        move_uploaded_file($_FILES['BackDesign']['tmp_name'], $target_path2);
        // wrong file type
        } else {echo $error =1; }
    } else { $target_path2 = 0; }       

echo "$target_path, $target_path2";
// PHPMailer
$mail = new PHPMailer();
$mail->addAddress('collegepregame@gmail.com');
$mail->SetFrom = "test@mail.com";
$mail->FromName = "Zach Cook";
$file_to_attach = $target_path;
$file_to_attach2 = $target_path2;
$mail->AddAttachment( $file_to_attach );
$mail->AddAttachment( $file_to_attach2 );
$mail->isHTML(true);
$mail->Subject = "Testing image send";
$mail->Body = "Does it work now?";
if(!$mail->send()) {
    echo 'Message could not be sent.';
}

但是，我不断得到一个"0"回声。这意味着代码因太大而无法通过测试，即使我知道它真的不是太大的文件。此外，文件未移动到新的文件位置。

这里看起来有什么问题？谢谢。