这是一篇非常好的文章，包含了关于jQuery表单提交你需要知道的一切。

文章摘要:

简单HTML表单提交

HTML:

<form action="path/to/server/script" method="post" id="my_form">
    <label>Name</label>
    <input type="text" name="name" />
    <label>Email</label>
    <input type="email" name="email" />
    <label>Website</label>
    <input type="url" name="website" />
    <input type="submit" name="submit" value="Submit Form" />
    <div id="server-results"><!-- For server results --></div>
</form>

JavaScript:

$("#my_form").submit(function(event){
    event.preventDefault(); // Prevent default action
    var post_url = $(this).attr("action"); // Get the form action URL
    var request_method = $(this).attr("method"); // Get form GET/POST method
    var form_data = $(this).serialize(); // Encode form elements for submission

    $.ajax({
        url : post_url,
        type: request_method,
        data : form_data
    }).done(function(response){ //
        $("#server-results").html(response);
    });
});

HTML Multipart/ Form -data表单提交

要将文件上传到服务器，我们可以使用XMLHttpRequest2提供的FormData接口，该接口构造一个FormData对象，可以使用jQuery Ajax轻松地将其发送到服务器。

HTML:

<form action="path/to/server/script" method="post" id="my_form">
    <label>Name</label>
    <input type="text" name="name" />
    <label>Email</label>
    <input type="email" name="email" />
    <label>Website</label>
    <input type="url" name="website" />
    <input type="file" name="my_file[]" /> <!-- File Field Added -->
    <input type="submit" name="submit" value="Submit Form" />
    <div id="server-results"><!-- For server results --></div>
</form>

JavaScript:

$("#my_form").submit(function(event){
    event.preventDefault(); // Prevent default action
    var post_url = $(this).attr("action"); // Get form action URL
    var request_method = $(this).attr("method"); // Get form GET/POST method
    var form_data = new FormData(this); // Creates new FormData object
    $.ajax({
        url : post_url,
        type: request_method,
        data : form_data,
        contentType: false,
        cache: false,
        processData: false
    }).done(function(response){ //
        $("#server-results").html(response);
    });
});

我希望这能有所帮助。

在提交前和提交成功后处理Ajax错误和加载器显示了一个警报引导框的示例:

var formData = formData;

$.ajax({
    type: "POST",
    url: url,
    async: false,
    data: formData, // Only input
    processData: false,
    contentType: false,
    xhr: function ()
    {
        $("#load_consulting").show();
        var xhr = new window.XMLHttpRequest();

        // Upload progress
        xhr.upload.addEventListener("progress", function (evt) {
            if (evt.lengthComputable) {
                var percentComplete = (evt.loaded / evt.total) * 100;
                $('#addLoad .progress-bar').css('width', percentComplete + '%');
            }
        }, false);

        // Download progress
        xhr.addEventListener("progress", function (evt) {
            if (evt.lengthComputable) {
                var percentComplete = evt.loaded / evt.total;
            }
        }, false);
        return xhr;
    },
    beforeSend: function (xhr) {
        qyuraLoader.startLoader();
    },
    success: function (response, textStatus, jqXHR) {
        qyuraLoader.stopLoader();
        try {
            $("#load_consulting").hide();

            var data = $.parseJSON(response);
            if (data.status == 0)
            {
                if (data.isAlive)
                {
                    $('#addLoad .progress-bar').css('width', '00%');
                    console.log(data.errors);
                    $.each(data.errors, function (index, value) {
                        if (typeof data.custom == 'undefined') {
                            $('#err_' + index).html(value);
                        }
                        else
                        {
                            $('#err_' + index).addClass('error');

                            if (index == 'TopError')
                            {
                                $('#er_' + index).html(value);
                            }
                            else {
                                $('#er_TopError').append('<p>' + value + '</p>');
                            }
                        }
                    });
                    if (data.errors.TopError) {
                        $('#er_TopError').show();
                        $('#er_TopError').html(data.errors.TopError);
                        setTimeout(function () {
                            $('#er_TopError').hide(5000);
                            $('#er_TopError').html('');
                        }, 5000);
                    }
                }
                else
                {
                    $('#headLogin').html(data.loginMod);
                }
            } else {
                //document.getElementById("setData").reset();
                $('#myModal').modal('hide');
                $('#successTop').show();
                $('#successTop').html(data.msg);
                if (data.msg != '' && data.msg != "undefined") {

                    bootbox.alert({closeButton: false, message: data.msg, callback: function () {
                            if (data.url) {
                                window.location.href = '<?php echo site_url() ?>' + '/' + data.url;
                            } else {
                                location.reload(true);
                            }
                        }});
                } else {
                    bootbox.alert({closeButton: false, message: "Success", callback: function () {
                        if (data.url) {
                            window.location.href = '<?php echo site_url() ?>' + '/' + data.url;
                        } else {
                            location.reload(true);
                        }
                    }});
                }

            }
        }
        catch (e) {
            if (e) {
                $('#er_TopError').show();
                $('#er_TopError').html(e);
                setTimeout(function () {
                    $('#er_TopError').hide(5000);
                    $('#er_TopError').html('');
                }, 5000);
            }
        }
    }
});

在你的php文件中输入:

$content_raw = file_get_contents("php://input"); // THIS IS WHAT YOU NEED
$decoded_data = json_decode($content_raw, true); // THIS IS WHAT YOU NEED
$bar = $decoded_data['bar']; // THIS IS WHAT YOU NEED
$time = $decoded_data['time'];
$hash = $decoded_data['hash'];
echo "You have sent a POST request containing the bar variable with the value $bar";

在你的js文件中发送一个带有数据对象的ajax

var data = { 
    bar : 'bar value',
    time: calculatedTimeStamp,
    hash: calculatedHash,
    uid: userID,
    sid: sessionID,
    iid: itemID
};

$.ajax({
    method: 'POST',
    crossDomain: true,
    dataType: 'json',
    crossOrigin: true,
    async: true,
    contentType: 'application/json',
    data: data,
    headers: {
        'Access-Control-Allow-Methods': '*',
        "Access-Control-Allow-Credentials": true,
        "Access-Control-Allow-Headers" : "Access-Control-Allow-Headers, Origin, X-Requested-With, Content-Type, Accept, Authorization",
        "Access-Control-Allow-Origin": "*",
        "Control-Allow-Origin": "*",
        "cache-control": "no-cache",
        'Content-Type': 'application/json'
    },
    url: 'https://yoururl.com/somephpfile.php',
    success: function(response){
        console.log("Respond was: ", response);
    },
    error: function (request, status, error) {
        console.log("There was an error: ", request.responseText);
    }
  })

或者保持表单提交的原样。只有当您希望发送带有计算附加内容的修改过的请求，而不仅仅是一些由客户机输入的表单数据时，才需要这种方法。例如哈希、时间戳、用户id、会话id等等。

这是使用ajax在HTML中填充选择选项标签的代码，而XMLHttpRequest和API是用PHP和PDO编写的

conn.php

<?php
$servername = "localhost";
$username = "root";
$password = "root";
$database = "db_event";
try {
    $conn = new PDO("mysql:host=$servername;dbname=$database", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    echo "Connection failed: " . $e->getMessage();
}
?>

category.php

<?php
 include 'conn.php';
try {
    $data = json_decode(file_get_contents("php://input"));
    $stmt = $conn->prepare("SELECT *  FROM events ");
    http_response_code(200);
    $stmt->execute();
    
    header('Content-Type: application/json');

    $arr=[];
    while($value=$stmt->fetch(PDO::FETCH_ASSOC)){
        array_push($arr,$value);
    }
    echo json_encode($arr);
   
  } catch(PDOException $e) {
    echo "Error: " . $e->getMessage();
  }

script.js

var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function () {
    if (this.readyState == 4 && this.status == 200) {
        data = JSON.parse(this.responseText);

        for (let i in data) {


            $("#cars").append(
                '<option value="' + data[i].category + '">' + data[i].category + '</option>'

            )
        }
    }
};
xhttp.open("GET", "http://127.0.0.1:8000/category.php", true);
xhttp.send();

index . html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <script src="https://code.jquery.com/jquery-3.6.0.min.js"
        integrity="sha256-/xUj+3OJU5yExlq6GSYGSHk7tPXikynS7ogEvDej/m4=" crossorigin="anonymous"></script>
    <title>Document</title>
</head>

<body>
    <label for="cars">Choose a Category:</label>

    <select name="option" id="option">
        
    </select>
    
    <script src="script.js"></script>
</body>

</html>

要使用jQuery发出Ajax请求，可以通过以下代码实现。

HTML:

<form id="foo">
    <label for="bar">A bar</label>
    <input id="bar" name="bar" type="text" value="" />
    <input type="submit" value="Send" />
</form>

<!-- The result of the search will be rendered inside this div -->
<div id="result"></div>

JavaScript:

方法1

 /* Get from elements values */
 var values = $(this).serialize();

 $.ajax({
        url: "test.php",
        type: "post",
        data: values ,
        success: function (response) {

           // You will get response from your PHP page (what you echo or print)
        },
        error: function(jqXHR, textStatus, errorThrown) {
           console.log(textStatus, errorThrown);
        }
    });

方法2

/* Attach a submit handler to the form */
$("#foo").submit(function(event) {
    var ajaxRequest;

    /* Stop form from submitting normally */
    event.preventDefault();

    /* Clear result div*/
    $("#result").html('');

    /* Get from elements values */
    var values = $(this).serialize();

    /* Send the data using post and put the results in a div. */
    /* I am not aborting the previous request, because it's an
       asynchronous request, meaning once it's sent it's out
       there. But in case you want to abort it you can do it
       by abort(). jQuery Ajax methods return an XMLHttpRequest
       object, so you can just use abort(). */
       ajaxRequest= $.ajax({
            url: "test.php",
            type: "post",
            data: values
        });

    /*  Request can be aborted by ajaxRequest.abort() */

    ajaxRequest.done(function (response, textStatus, jqXHR){

         // Show successfully for submit message
         $("#result").html('Submitted successfully');
    });

    /* On failure of request this function will be called  */
    ajaxRequest.fail(function (){

        // Show error
        $("#result").html('There is error while submit');
    });

从jQuery 1.8开始，.success()、.error()和.complete()回调函数已弃用。要为最终删除它们做好准备，请使用.done()、.fail()和.always()来代替。

MDN: abort()。如果请求已经发送，此方法将中止请求。

我们已经成功地发送了一个Ajax请求，现在是时候向服务器抓取数据了。

PHP

当我们在Ajax调用中发出POST请求(类型:" POST ")时，我们现在可以使用$_REQUEST或$_POST获取数据:

  $bar = $_POST['bar']

您还可以通过以下两种方式查看您在POST请求中获得了什么。顺便说一句，确保设置了$_POST。否则您将得到一个错误。

var_dump($_POST);
// Or
print_r($_POST);

您正在向数据库中插入一个值。确保在执行查询之前正确地敏感或转义了所有请求(无论是GET还是POST)。最好的方法是使用准备好的语句。

如果你想将任何数据返回到页面，你可以通过如下所示的回显数据来实现。

// 1. Without JSON
   echo "Hello, this is one"

// 2. By JSON. Then here is where I want to send a value back to the success of the Ajax below
echo json_encode(array('returned_val' => 'yoho'));

然后你可以得到:

 ajaxRequest.done(function (response){
    alert(response);
 });

有几种简便的方法。您可以使用下面的代码。它做同样的功。

var ajaxRequest= $.post("test.php", values, function(data) {
  alert(data);
})
  .fail(function() {
    alert("error");
  })
  .always(function() {
    alert("finished");
});

HTML:

    <form name="foo" action="form.php" method="POST" id="foo">
        <label for="bar">A bar</label>
        <input id="bar" class="inputs" name="bar" type="text" value="" />
        <input type="submit" value="Send" onclick="submitform(); return false;" />
    </form>

JavaScript:

   function submitform()
   {
       var inputs = document.getElementsByClassName("inputs");
       var formdata = new FormData();
       for(var i=0; i<inputs.length; i++)
       {
           formdata.append(inputs[i].name, inputs[i].value);
       }
       var xmlhttp;
       if(window.XMLHttpRequest)
       {
           xmlhttp = new XMLHttpRequest;
       }
       else
       {
           xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
       }
       xmlhttp.onreadystatechange = function()
       {
          if(xmlhttp.readyState == 4 && xmlhttp.status == 200)
          {

          }
       }
       xmlhttp.open("POST", "insert.php");
       xmlhttp.send(formdata);
   }