run javascript function only if php conditions are met

Question

I want the start_uploading function only to start if all the conditions are met and the file is uploading, right now the 'loading' message pops up for a split second when the form is submitted but it did not meet all the conditions to upload.

if(condtion){// don't start function} else

if(move_uploaded_file($_FILES['uploaded']['tmp_name'], $target)) {
  //now start function} else echo "error";

javascript

function start_Uploading(){
  document.getElementById('message').innerHTML = 'Loading... <br> Please Wait';
  return true;
}

and html

<form action="something.php" method="POST" enctype="multipart/form-data"
 onsubmit="start_Uploading();">

What will you do when Javascript is disabled in the browser? — samayo
– samayo, Commented Jan 13, 2013 at 0:37

Dennis Hackethal · Accepted Answer · 2013-01-13 00:37:33Z

2

Since you are checking for the condition to be true in php, I would simply only echo out the js method name if the condition is met.

Like so:

<?php
  if(true) $onsubmit = "start_Uploading();"; // Put actual condition in parantheses
  else $onsubmit = "";
?>

And then in your form:

<form action="something.php" method="POST" enctype="multipart/form-data"
onsubmit="<?php echo $onsubmit; ?>">

If the condition isn't met, no method name will be provided and js simply won't know what to look for on submit.

answered Jan 13, 2013 at 0:37

Dennis Hackethal

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3 Comments

user1559811 Over a year ago

Thanks for the code, I tried it but it only seems to be effective on form re-submission

Dennis Hackethal Over a year ago

Please have a look at the pages sourcecode in the browser - does the method name appear if the condition is met? If so, there may still be an error in your js - if not, please tell us specifically what else you can find out.

user1559811 Over a year ago

I figured it out now, it only recognizes the variable after uploading by which time its to late to be used in the html, violating cause and effect. I'll have to figure out a different tactic, Thanks for the code though

Taha Paksu · Accepted Answer · 2013-01-13 00:46:14Z

1

move_uploaded_file() is copying the uploaded file from apache's temp directory to user directory, so when you submit the file, so it would be already uploaded to the temp directory before the php side can start processing that file.

So, I recommend you to use a client side (javascript) form validation, or make a research about AJAX file uploads and/or form validation. PHP is a server side language, and runs before a page loads. Not inside a page. (Unless it's an AJAX call from client.)

answered Jan 13, 2013 at 0:46

Taha Paksu

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