Passing data from PHP to JavaScript

A drawing of a cartoon man pointing upwards

Heads up! This post was written in 2015, so it may contain information that is no longer accurate. I keep posts like this around for historical purposes and to prevent link rot, so please keep this in mind as you're reading.

— Cory

Have you ever needed to send a PHP variable, array, or object to JavaScript? It can get complicated trying to escape the output properly. Here's a way that always works—no escaping necessary.

Let's say we have the following variable in PHP:

$name = 'Bob Marley';

And we want to pass it to a JavaScript variable called name. Here's the trick:

echo '<script>';
echo 'var name = ' . json_encode($name) . ';';
echo '</script>';

Using json_encode(), you'll always get a properly formatted JavaScript object.

The same trick can be applied to other data types (e.g. integers, arrays, objects, etc.). The following passes an entire array from PHP to JavaScript:

$shirt = array(
  'color' => 'blue',
  'number' => 23,
  'size' => 'XL'

echo '<script>';
echo 'var shirt = ' . json_encode($shirt) . ';';
echo '</script>';

The output looks like this:

<script>var shirt = {"color":"blue","number":23,"size":"XL"}</script>

Don't want it all on one line? Try this instead:

echo "<script>\n";
echo 'var shirt = ' . json_encode($shirt, JSON_PRETTY_PRINT) . ';';
echo "\n</script>";

The output is a bit easier to read:

var shirt = {
  "color": "blue",
  "number": 1000,
  "size": "XL"

A simple trick, but nevertheless useful.