HTML 中按钮作为form表单元素提交特性两则 --- 参HTML考标准分析
相同name的submit 类型的input提交行为
描述
这种情况，
<input type="submit" name="ACTION" value="Apply"/>
<input type="submit" name="ACTION" value="Cancel"/>
其能够作为提交内容， 发送到服务器段的参数的按钮， 对应被点击激活的按钮。
这表示多个 同名的name， 一次提交只能激活一个。
例如点击了 apply， ACTION=Apply会被传送到服务器端。 这样服务器端就可以判断对于同样提交的一份数据，
需要执行什么样的操作， 是修改， 还是删除？
Code
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>phpStudy 探针 2014 </title>
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
<form method="post">
<textarea>
<?php
echo "IF_ACTION=" . $_POST['IF_ACTION'];
echo "data=" . $_POST['data'];
?>
</textarea>
<input type="text" name="data" value="data"/>
<input type="submit" name="IF_ACTION" value="Apply"/>
<input type="submit" name="IF_ACTION" value="Cancel"/>
</form>
</body>
</html>
标准解读
https://www.w3.org/TR/html4/interact/forms.html#current-value
见下面段落中（关于form表单中 successful control的定义），这一句：
If a form contains more than one submit button, only the activated submit button is successful.
所有的 提交按钮中， 只能被激活的那个按钮， 是successful的， 即可以提交到服务器端。
段落：
17.13.2 Successful controls
A successful control is "valid" for submission. Every successful control has its control name paired with its current value as part of the submitted form data set. A successful control must be defined within a FORM element and must have a control name.
However:
- Controls that are disabled cannot be successful.
- If a form contains more than one submit button, only the activated submit button is successful.
- All "on" checkboxes may be successful.
- For radio buttons that share the same value of the name attribute, only the "on" radio button may be successful.
- For menus, the control name is provided by a SELECT element and values are provided by OPTION elements. Only selected options may be successful. When no options are selected, the control is not successful and neither the name nor any values are submitted to the server when the form is submitted.
- The current value of a file select is a list of one or more file names. Upon submission of the form, the contents of each file are submitted with the rest of the form data. The file contents are packaged according to the form's content type.
- The current value of an object control is determined by the object's implementation.
类型为 button 的 input为什么不能提交 ？
描述
如果有一个button类型的按钮存在与form中， 则form被提交， 其提交的参数中， 不会存在 这个按钮的 name 和 value。
如下代码： pushbutton 在请求的数据中不存在。
<form id="fileupload" name="fileupload" method="post" action="/index.php">
<input type="file" name="testfile" multiple="multiple"></br>
<input type="text" name="textinput" value="textinputvalue"></br>
<input type="button" name="pushbutton" value="pushbutton">
<input type="submit" name="submit" value="upload"></br>
</form>
Code
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script src="./jquery.js"></script>
<link rel="stylesheet" href="./test.css" />
</head>
<body>
<style>
</style>
<form id="fileupload" name="fileupload" method="post" action="/index.php">
<input type="file" name="testfile" multiple="multiple"></br>
<input type="text" name="textinput" value="textinputvalue"></br>
<input type="button" name="pushbutton" value="pushbutton">
<input type="submit" name="submit" value="upload"></br>
</form>
<script>
document.write("enctype="+document.getElementById("fileupload").getAttribute("enctype").toLowerCase());
</script>
</body>
</html>
标准分析
https://www.w3.org/TR/html401/interact/forms.html#buttons
标准对button的解释， 很清楚了， 包括三种类型：
1、 提交类型 ( 用于提交表单数据， 用户点击提交按钮 ， 或者光标表单内点击键盘的enter键盘 -- IE实现是第一个submit按钮提交被触发 )
2、 重置类型( reset button - 不用与后台交互， 就可以将页面控件的默认值， 现实出来， 即HTML value attribute的值。 )
3、 推送类型（push button - 不执提交和重置， 需要绑定js处理事件， 例如将表单参数校验成功后再提交form）
鉴于它的类型作用， 其确实没有必要提交， reset按钮也类似。
buttons Authors may create three types of buttons:
- submit buttons: When activated, a submit button submits a form. A form may contain more than one submit button.
- reset buttons: When activated, a reset button resets all controls to their initial values.
- push buttons: Push buttons have no default behavior. Each push button may have client-side scripts associated with the element's event attributes. When an event occurs (e.g., the user presses the button, releases it, etc.), the associated script is triggered.
Authors should specify the scripting language of a push button script through a default script declaration (with the META element).
Authors create buttons with the BUTTON element or the INPUT element. Please consult the definitions of these elements for details about specifying different button types.
Note. Authors should note that the BUTTON element offers richer rendering capabilities than the INPUT element.
