Passing PHP variable to vue.js vue component

Hi everyone, I am working on a php site where I want to pass a php string variable to be used in a .vue component. Can someone help me wit this?

here is what i have in code: index.php

<?php 
$foo = 72;
?>

<div id='app'></div>

app.js

import App from './views/App';
new Vue({
  el: '#app',
  render: h => h(App)
});

App.vue

<template>

</template>

<script>
export default {
name: 'App',
 data() {
  return {
   foo: ''
  }
 }
}
</script>

<style></style>

As you can see in index.php, $foo = 72. I want that 72 value will be pass on to $foo in App.vue