php数组到json数组（使用sendgrid）

I would like to use a php array in this example rather than have to hard code the array. How would I use a php to replace this json example?

Here the working code with the json array:

$json_string = array(

  'to' => array(
    'example1@sendgrid.com', 'example2@sendgrid.com'
  ),
  'category' => 'test_category'
);

But I need to replace the 'to' values with my own php array. I tried this but it doesn't work:

$myEmails[] = array('emailOne@gmail.com','email2@gmail.com');
$json_string = array(

  'to' => $myEmails, /// DOES NOT WORK
  'category' => 'test_category'
);

What code for the json could I use to add my own php array values here? In short I am trying to send multiple emails using sendgrid but I thought this might work but its not.

Just get rid of the square braces [] after $myEmails, and everything should work:

<?php 
  $myEmails = array('emailOne@gmail.com','email2@gmail.com');
  $json_string = array(
    'to' => $myEmails, /// DOES NOT WORK
    'category' => 'test_category'
  );
  var_dump($json_string);
?>