无法使用 $_FILES 过程在 PHP 中上传图像

我正在使用 PHP $_FILE 过程将图像上传到特定文件夹，但没有任何反应，我也尝试使用一些片段，但似乎没有任何效果，我正在使用 PHP 和 JavaScript 来做到这一点，

这是PHP代码：

<?php
if (isset($_POST['postImage']))
    {
    $validextensions = array(
        "jpeg",
        "jpg",
        "png",
        "gif"
    );
    $temporary = explode(".", $_FILES["postImage"]["name"]);
    $file_extension = end($temporary);
    if ((($_FILES["postImage"]["type"] == "../news/img/.png") || ($_FILES["postImage"]["type"] == "../news/img/.jpg") || ($_FILES["postImage"]["type"] == "../news/img/.jpeg") || ($_FILES["postImage"]["type"] == "../news/img/.gif")) && in_array($file_extension, $validextensions))
        {
        if ($_FILES["postImage"]["error"] > 0)
            {
            echo "Return Code: " . $_FILES["postImage"]["error"] . "<br/><br/>";
            }
          else
            {
            echo "<span>Your File Uploaded Succesfully...!!</span><br/>";
            echo "<br/><b>File Name:</b> " . $_FILES["postImage"]["name"] . "<br />";
            echo "<b>Type:</b> " . $_FILES["postImage"]["type"] . "<br />";
            echo "<b>Temp file:</b> " . $_FILES["postImage"]["tmp_name"] . "<br />";
            if (file_exists("../news/img/" . $_FILES["postImage"]["name"]))
                {
                echo $_FILES["postImage"]["name"] . " <b>already exists.</b> ";
                }
              else
                {
                move_uploaded_file($_FILES["postImage"]["tmp_name"], "../news/img/" . $_FILES["postImage"]["name"]);
                echo "<b>Stored in:</b> " . "../news/img/" . $_FILES["postImage"]["name"];
                }
            }
        }
      else
        {
        echo "<span>***Invalid file Size or Type***<span>";
        }
    }
?>

JavaScript 代码：

<script>
        $(document).ready(function() {
        // Function for Preview Image.
        $(function() {
        $(":file").change(function() {
        if (this.files && this.files[0]) {
        var reader = new FileReader();
        reader.onload = imageIsLoaded;
        reader.readAsDataURL(this.files[0]);
        }
        });
        });
        function imageIsLoaded(e) {
        $('#message').css("display", "none");
        $('#preview').css("display", "block");
        $('#previewimg').attr('src', e.target.result);
        };
        // Function for Deleting Preview Image.
        $("#deleteimg").click(function() {
        $('#preview').css("display", "none");
        $('#file').val("");
        });
        // Function for Displaying Details of Uploaded Image.
        $("#submit").click(function() {
        $('#preview').css("display", "none");
        $('#message').css("display", "block");
        });
        });
    </script>

该 HTML 代码：

 <form action="" method="post">  
   <div id="message"></div>
   <input id="postImage" type="file" name="postImage" placeholder="Upload Image" value="">
   <input type="submit">
   <br>
   <br>
   <div id="preview">
      <img id="previewimg" src="">
   </div>
 </form>