are function args in exceptions traced passed by reference?

gistfile1.php

<?php
# Example for https://gerrit.wikimedia.org/r/#/c/92334/

function blame($a) {
    throw new Exception();
}

try {
    blame( array('foobar') );
} catch (Exception $e) {
    var_dump( $e->getTrace() );
}

__HALT_COMPILER(); ?>

Above script yield:

$ php foo.php 
array(1) {
  [0]=>
  array(4) {
    ["file"]=>
    string(54) "/Users/amusso/projects/mediawiki/core/includes/foo.php"
    ["line"]=>
    int(7)
    ["function"]=>
    string(5) "blame"
    ["args"]=>
    array(1) {
      [0]=>
      array(1) {
        [0]=>
        string(6) "foobar"
      }
    }
  }
}