Cant echo PHP variable inside

Question

This is my PHP code. I want error to be displayed using an alert window.

 if ($projectid=="")
  {
    $error = 'You must choose a project.
              Click &lsquo;back&rsquo; and try again.';
    include error.html.php';
    exit();
  }

This is error.html.php that is supposed to be parsed by the browser

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>Script Error</title>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1">


    </head>

    <body>

         <script> 
             var error = <?php echo   $error ; ?>;
              window.onload = function(){ alert(error); }
         </script>
    </body>
</html>

Wahts up with the script tags ? Do they prevent PHP from running ?

Niet the Dark Absol · Accepted Answer

The real problem is that this is what your rendered result looks like:

var error = You must choose a project.
            Click &lsquo;back&rsquo; and try again.

Does that looks like valid JavaScript to you? I think not.

var error = <?=json_encode($error);?>;

That should result in:

var error = "You must choose a project.
                 Click &lsquo;back&rsquo; and try again.";

Much better.

mseifert · Answer

Your problem is that javascript is run on the client and will run after the page loads and so after the php is run on the server.

However, you can do something like the following which allows php to set the value of a javascript variable when the page loads and then AFTER the page is loaded runs the javascript to display the message.

<?php 
$error = "test me";
echo "<script>error = '" . $error  . "'</script>";
?>

<script>
var error;
window.onload = function(){
    alert(error);
}

</script>

UPDATE Based on your edits, here's an updated answer. The echo "<script>error = '" . $error . "'</script>" is needed to assign the $error to the javascript variable when the page is loaded.

if ($projectid=="")
  {
    $error = 'You must choose a project.
              Click ‘back’ and try again.';
    echo "<script>error = '" . json_encode($error)  . "'</script>"
    include error.html.php';
    exit();
}

And the html

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <title>Script Error</title>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1">


    </head>

    <body>

         <script> 
             var error;
              window.onload = function(){ alert(error); }
         </script>
    </body>
</html>

Cant echo PHP variable inside <script> tags? [closed]

Tags:

json

javascript

html

php

marc

2 Answers

Niet the Dark Absol

mseifert

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