如何在单击下载按钮时将mysql数据库中的值保存到txt文件中?

<p>Here are all the jokes in the database:</p> <?php foreach ($jokes as $joke): ?> <blockquote><p> <?php echo htmlspecialchars($joke, ENT_QUOTES, 'UTF-8'); ?> </p></blockquote> <?php endforeach; ?>

如果修改页面的HTML/PHP部分,使其包含这样一个简单的超链接:

<p>Here are all the jokes in the database:</p>  
<?php foreach ($jokes as $id => $joke): ?>  
  <blockquote>
      <p>  
        <?php 
            echo htmlspecialchars($joke, ENT_QUOTES, 'UTF-8');
        ?>
      </p>
      <a class='download' href='#' title='Download the joke'>Download</a>
  </blockquote>  
<?php endforeach; ?>

<html>
    <head>
        <title>Download a joke</title>
        <script>
            /*
                wait for the DOM to load and then set event listeners
                on the new hyperlinks
            */
            document.addEventListener('DOMContentLoaded', ()=>{
                /*
                    Query the DOM for ALL hyperlinks of class `download`
                    and assign an event handler for click events
                */
                document.querySelectorAll('a.download').forEach( function(a){
                    a.addEventListener( 'click', function( event ){
                        /*
                            prevent the default action for this hyperlink
                        */
                        event.preventDefault();

                        /*
                            The Joke is located in the previous
                            DOM node - P
                        */
                        let p=this.previousElementSibling;

                        /*
                            create a BLOB object to store the joke text
                        */
                        let blob=new Blob([ p.innerText ],{type: 'text/plain'});


                        /*
                            function to send the file - jiggery pokery
                        */
                        const sendfile=function( blob, name ){
                            let url=URL.createObjectURL( blob );
                            let lnk=document.createElement('a');
                            let evt=new MouseEvent('click',{
                                bubbles:true,
                                cancelable:true,
                                view:window
                            });
                            p.appendChild( lnk );
                            lnk.href=url;
                            lnk.download=name;
                            lnk.dispatchEvent( evt );
                            p.removeChild( lnk );
                        }


                        sendfile.call( this, blob, 'joke.txt' );
                    });
                });
            });
        </script>
    </head>
    <body>

        <!-- EXAMPLE DATA -->
        <blockquote>
            <p>  
                This is the joke - not very funny though is it?
            </p>
            <a class='download' href='#' title='Download the joke'>Download</a>
        </blockquote>

        <blockquote>
            <p>  
                This is another joke - or what passes for a joke!
            </p>
            <a class='download' href='#' title='Download the joke'>Download</a>
        </blockquote>

        <blockquote>
            <p>  
                This is probably not the best joke in the World.
            </p>
            <a class='download' href='#' title='Download the joke'>Download</a>
        </blockquote>

        <blockquote>
            <p>  
                A woman gets on a bus with her baby. The bus driver says: 'Ugh, that's the ugliest 
                baby I've ever seen!' The woman walks to the rear of the bus and sits down, fuming. 
                She says to a man next to her: 'The driver just insulted me!' The man says: 'You go 
                up there and tell him off. Go on, I'll hold your monkey for you.
            </p>
            <a class='download' href='#' title='Download the joke'>Download</a>
        </blockquote>


    </body>
</html>