PHP form development back-end PHP source code writing

<?php
if (in_array($_FILES["file"]["type"], array("image/gif", "image/jpeg","image/jpg"))) {  //对上传图片格式进行限定
    
    if ($_FILES["file"]["error"] > 0)                         //由文件上传导致的错误提示代码
    {
        echo "Return Code: " . $_FILES["file"]["error"] . "<br />";    //错误输出
    }
    else                                                                 
    {
        echo "Upload: " . $_FILES["file"]["name"] . "<br />";          //正确输出
        echo "Type: " .  $_FILES["file"]["type"] . "<br />";
        echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
        echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br />";
        
        if (file_exists("upload/" . $_FILES["file"]["name"]))        //对上传至文件夹upload的文件进行判断
        {
            echo $_FILES["file"]["name"] . " already exists. ";
        }
        else
        {
            move_uploaded_file($_FILES["file"]["tmp_name"],                   // 存储在服务器的文件的临时副本的名称
                "upload/" . $_FILES["file"]["name"]);
            echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
        }
    }
}
else
{
    echo "Invalid file";
}
?>

Restrict the format of image uploading—>Judge whether there is an error in uploading (1. Output the content in error, 2. Output the content correctly)—>Judge whether the picture is valid

The general idea is as written above, in addition This code can also be optimized. The optimized code:

<?php
if (count($_FILES)) {
    $retFiles = uploadFile("file");
    if ($retFiles['status'] == 1) {
        echo $retFiles['message'];
    } else if ($retFiles['status'] == 0) {
        echo "Upload: " . $retFiles["name"] . "<br />";
        echo "Type: " .  $retFiles["type"] . "<br />";
        echo "Size: " . ($retFiles["size"] / 1024) . " Kb<br />";
        echo "Temp file: " . $retFiles["temp"] . "<br />";
        echo "Stored in: " . "upload/" . $retFiles["name"];
    }
}
function uploadFile($fileName)
{
    $files = $_FILES[$fileName];
    if (!in_array($files["type"], array("image/gif","image/jpeg","image/pjpeg","image/jpeg", "image/png"))) {
        return array("status" => 1, "message" => "Uploaded image format is not correct");
    }
    
    if ($files["error"] > 0) {
        return array("status" => 1, "message" => "upload error");
    }
    if (file_exists("upload/" . $files["name"])) {
        return array("status" => 1, "message" => $files["name"]." already exiss");
    }
    move_uploaded_file($files["tmp_name"], "upload/".$files["name"]);
    return array("status" => 0, "name" => $files["name"], "type" => $files["type"], "size" => $files['size']/1024, "temp" => $files["tmp_name"]);
}
?>

The second method uses functions, which is simpler and more beautiful to write, but not as easy to understand as the first method.