Why, when I pass the selected option in a dropdown to PHP through Ajax, does it always give me the first option?_问答_开发者

Why, when I pass the selected option in a dropdown to PHP through Ajax, does it always give me the first option?

开发者 https://www.devze.com 2023-01-21 07:53 出处：网络

This is my code: <html> <head> <script> comenzar = function(){ document.getElementById(\'gene\').onclick = xmlhttpPost(\"generador.php\");

This is my code:

<html>
    <head>
        <script>
            comenzar = function(){
                document.getElementById('gene').onclick = xmlhttpPost("generador.php");
            }

            xmlhttpPost = function(strURL){
                xmlHttpReq = false;
                self = this;
                self.xmlHttpReq = new XMLHttpRequest();
                self.xmlHttpReq.open('POST', strURL, true);
                self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
                self.xmlHttpReq.onreadystatechange = function(){
                    if(self.xmlHttpReq.readyState == 4){
                        update(self.xmlHttpReq.responseText);
                    }
                }
                self.xmlHttpReq.send(getquerystring());
            }

            getquerystring = function(){
                form = document.getElementById('formu');
                combi = document.getElementById('sele').options[document.getElementById('sele').selectedIndex].value;
                qstr = "tres=" + escape(combi);
                return qstr;
            }

            update = 开发者_StackOverflow社区function(resu){
                document.getElementById('tag').innerHTML = resu;
            }
            window.onload = comenzar;
        </script>
    </head>

    <body>
        <form id=formu>
            <select id=sele>
                <option>C</option>
                <option>v</option>
            </select>
            <button id=gene><p>generate</p></button>
        </form>
        <p id=tag></p>
    </body>
</html>

//generador.php
<?php
    echo( "tu combinacion" . $_POST['tres'] );
?>

The problem is not the getting of the value. The hook are these two things:

document.getElementById('gene').onclick = xmlhttpPost("generador.php");

...you may think that you set something to be executed to the onclick-Event of the button, but you don’t. This function will be executed immediately, not onclick.

You should write it that way:

document.getElementById('gene').onclick = function(){xmlhttpPost("generador.php");}

The other problem:

The default type of a <button> is submit, so if you click on the button, the form will be sent. You can either set the type of the button to "button" or cancel the submitting of the form via JavaScript, otherwise your Ajax request is useless, because the form will be sent (and the page reloaded).