javascript not accepting boolean or null from php

Question

I am trying to learn javascript. I have the following code:

<?php
    $a = true;
    $b = false;
?>


<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
    <script>
        window.variable = {
            a: <?php $a ? true : false ?>,
            b: <?php $b ? 1 : null ?>
        }

        console.log(variable);
    </script>
</body>
</html>

Javascript is not accepting the true, fasle, 1 or null I am getting the Uncaught SyntaxError: Unexpected token , and it is displaying the following in the chrome dev tools:

<script>
    window.variable = {
    a: ,
    b:      }

    console.log(variable);
</script>

where am I going wrong??

the `` tag is for executing php only. It do not output anything to the document. You need to use [echo or =php ...?>](http://php.net/manual/fr/function.echo.php) — litelite, Jul 14 '17 at 19:40

score 1 · Accepted Answer · answered Jul 14 '17 at 19:42

a: <?php $a ? true : false ?>,
b: <?php $b ? 1 : null ?>

First, you're not outputting anything. You need to echo things.

Second, the string representation of false is an empty string. Same thing for null. So, even with echo, you'll get empty outputs for some values of $a and $b, and the same JS syntax error.

You can fix the output by outputting the strings true, false, and null:

a: <?php echo $a ? 'true' : 'false' ?>,
b: <?php echo $b ? 1 : 'null' ?>

but for a more resilient approach, since you're outputting for use in JavaScript, use json_encode instead:

a: <?php echo json_encode($a ? true : false) ?>,
b: <?php echo json_encode($b ? 1 : null) ?>

or, even better, have PHP output the whole JS object:

window.variable = <?php echo json_encode([
    'a' => $a ? true : false,
    'b' => $b ? 1 : null,
]); ?>;

score 0 · Answer 2 · answered Jul 14 '17 at 19:47

Remember that you're building text; use "echo" to output the right value as a string.

<?php
  $a = true;
  $b = false;
?>


<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title></title>
</head>
<body>
    <script>
        window.variable = {
            a: <?php echo $a ? "true" : "false" ?>,
            b: <?php echo $b ? "1" : "null" ?>
        }

        console.log(variable);
    </script>
</body>
</html>

javascript not accepting boolean or null from php

2 Answers2