php网站上传

<?php
if ($_FILES["file"]["error"] > 0) {
    echo "Error: " . $_FILES["file"]["error"] . "<br>";
} else {
    $allowedExts = array("gif", "jpeg", "jpg", "png");
    $temp = explode(".", $_FILES["file"]["name"]);
    $extension = end($temp);
    if ((($_FILES["file"]["type"] == "image/gif")
    || ($_FILES["file"]["type"] == "image/jpeg")
    || ($_FILES["file"]["type"] == "image/jpg")
    || ($_FILES["file"]["type"] == "image/pjpeg")
    || ($_FILES["file"]["type"] == "image/x-png")
    || ($_FILES["file"]["type"] == "image/png"))
    && ($_FILES["file"]["size"] < 20000)
    && in_array($extension, $allowedExts)) {
        if ($_FILES["file"]["error"] > 0) {
            echo "Return Code: " . $_FILES["file"]["error"] . "<br>";
        } else {
            echo "Upload: " . $_FILES["file"]["name"] . "<br>";
            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"])) {
                echo $_FILES["file"]["name"] . " already exists. ";
            } else {
                move_uploaded_file($_FILES["file"]["tmp_name"],
                "upload/" . $_FILES["file"]["name"]);
                echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
            }
        }
    } else {
        echo "Invalid file";
    }
}
?>