如何停止刷新页面的JavaScript警报？

Question

I am teaching myself, so I apologize in advance if this is a 'newbie' question, but I have searched the internet and cannot find a solution.

So I've created a HTML form, and in that form I have added a Dropzone.js where people upload a file. When finished they click a button which saves it into a MySQL form, that all works great. The issue is when people click the button before the file finishes uploading. To counteract this issue, I've created an 'If Statement' that checks if the uploaded file exists. If it hasn't uploaded, then a JavaScript alert is triggered, which all works, but it refreshes the page, which erases all the imputed data.

// This is when the button is clicked
if(isset($_POST['Upload'])){
    if (file_exists(blah blah) {

        //All my MySQL stuff is in here



    //If it isn't uploaded 
    } else {
        echo '<script language="javascript">';
        echo 'alert("Please upload at least one file")';
        echo 'return false';
        echo '</script>';
    }}

Despite the 'return false'; it still resets the page?

Any help would be appreciated, thanks!

Answer 1

Can you show me the all code. You can do it with lots of methods i do it with validation. you can set a variable which increase on file upload. if variable value zero then return false form will not submit.

Php does not support like this echo 'return false'. you have to use JavaScript validation for this purpose.