php ajax上传不起作用

Question

I want to upload image using php and ajax jquery, but i got problem, first if on submit by #uploadimage form, the form process the action not the ajax whatever I remove that action.second if the button i change to type button and javascript function .submit on click function ajax called but the $_FILES not set because image not save and there is nothing output message

the view

<form id="uploadimage" action="http://localhost/pkh/mod/page/tpl/ajax_php_file.php" method="post" enctype="multipart/form-data">
       <input type="file" name="file" id="file" required />
       <input type="submit" value="Upload" class="submit" />
</form>

the js

<script type="text/javascript">
    $(document).ready(function (e) {
        $("#uploadimage").submit(function(e) {
            e.preventDefault();
            $("#message").empty();
            $('#loading').show();
            $.ajax({
                url: "http://localhost/pkh/mod/page/tpl/ajax_php_file.php", // Url to which the request is send
                type: "POST",             // Type of request to be send, called as method
                data: new FormData(this), // Data sent to server, a set of key/value pairs (i.e. form fields and values)
                contentType: false,       // The content type used when sending data to the server.
                cache: false,             // To unable request pages to be cached
                processData:false,        // To send DOMDocument or non processed data file it is set to false
                success: function(data)   // A function to be called if request succeeds
                {
                    $('#loading').hide();
                    $("#message").html(data);
                }
            });
        });

        // Function to preview image after validation
        $(function() {
            $("#file").change(function() {
                $("#message").empty(); // To remove the previous error message
                var file = this.files[0];
                var imagefile = file.type;
                var match= ["image/jpeg","image/png","image/jpg"];
                if(!((imagefile==match[0]) || (imagefile==match[1]) || (imagefile==match[2])))
                {
                    $('#previewing').attr('src','noimage.png');
                    $("#message").html("<p id='error'>Please Select A valid Image File</p>"+"<h4>Note</h4>"+"<span id='error_message'>Only jpeg, jpg and png Images type allowed</span>");
                    return false;
                }
                else
                {
                    var reader = new FileReader();
                    reader.onload = imageIsLoaded;
                    reader.readAsDataURL(this.files[0]);
                    }
            });
        });
        function imageIsLoaded(e) {
            $("#file").css("color","green");
            $('#image_preview').css("display", "block");
            $('#previewing').attr('src', e.target.result);
            $('#previewing').attr('width', '400px');
            $('#previewing').attr('height', '252px');
        };
    });

</script>

the php

<?php

     if(isset($_FILES["file"]["type"]))
    {
        $validextensions = array("jpeg", "jpg", "png");
        $temporary = explode(".", $_FILES["file"]["name"]);
        echo $_FILES["file"]["type"];
        echo $_FILES["file"]["name"];

        $file_extension = end($temporary);
        if ((($_FILES["file"]["type"] == "image/png") || ($_FILES["file"]["type"] == "image/jpg") || ($_FILES["file"]["type"] == "image/jpeg")
        ) && ($_FILES["file"]["size"] < 100000)//Approx. 100kb files can be uploaded.
        && in_array($file_extension, $validextensions)) 
        {
            if ($_FILES["file"]["error"] > 0)
            {
                echo "Return Code: " . $_FILES["file"]["error"] . "<br/><br/>";
            }
            else
            {
                if (file_exists("http://localhost/pkh/data/files/ktp/" . $_FILES["file"]["name"])) 
                {
                    echo $_FILES["file"]["name"] . " <span id='invalid'><b>already exists.</b></span> ";
                }
                else
                {
                    $sourcePath = $_FILES['file']['tmp_name']; // Storing source path of the file in a variable
                    $targetPath = "http://localhost/pkh/data/files/ktp/".$_FILES['file']['name']; // Target path where file is to be stored
                    move_uploaded_file($sourcePath,$targetPath) ; // Moving Uploaded file
                    echo "<span id='success'>Image Uploaded Successfully...!!</span><br/>";
                    $namaFile = basename( $_FILES["file"]["name"]);

                    $q = " UPDATE SET tbl_applicant fileKTP = '{$namaFile}' where applicantID = '{$userinfo['applicantID']}'";
                    $APPOBJECT->query($q);

                    echo "<br/><b>File Name:</b> " . $_FILES["file"]["name"] . "<br>";
                    echo "<b>Type:</b> " . $_FILES["file"]["type"] . "<br>";
                    echo "<b>Size:</b> " . ($_FILES["file"]["size"] / 1024) . " kB<br>";
                    echo "<b>Temp file:</b> " . $_FILES["file"]["tmp_name"] . "<br>";
                }
            }
        }
        else
        {
            echo "<span id='invalid'>***Invalid file Size or Type***<span>";
        }
    }
?>