How to send data from a PHP variable to JavaScript by Ajax?

Is the following code correct?

 $.ajax( {
             url: './ajax/aj开发者_运维技巧ax_addTerms.php',
             type: 'POST',
             data: {"fId" : $fId, "term" : $term, "alias" : $alias,
 "userId" : <?php  print $userId; ?>},

When I remove the PHP tags it works, but this way it doesn't.

Wrap the value like this:

 "userId" : "<?php  print $userId; ?>"}

Otherwise JS will try to parse the PHP output which is wrong.

 $.ajax( {
             url: './ajax/ajax_addTerms.php',
             type: 'POST',
             data: {"fId" : <?php echo $fId ?>, "term" : "<?php echo $term ?>", "alias" : "<?php echo $alias ?>",
 "userId" : <?php echo $userId; ?>},
 // echo is faster than print
 // and I assume $fId and $userId are integers so quotes aren't required

PHP's interpreter will parse variables and then JS does the rest.

I would use json_encode additionally to the <?php ?> to make sure that " in a string gets escaped properly:

data: {"fId" : <?php echo json_encode($fId); ?>, "term" : <?php echo json_encode($term) ?>, "alias" : <?php echo json_encode($alias); ?>, "userId" : <?php echo $userId; ?>},

This way, you could also pass an array:

<?php $data = array('fId' => $fId, 'term' => $term, 'alias' => $alias, 'userId' => $userId); ?>
...
data: <?php echo json_encode($data); ?>, // Same result as above

JavaScript is client side, PHP is server side. Ajax works like this,

JavaScript HTTP request --> PHP --> return request that is catched by the Ajax handler.

You can't start Ajax from the server side.