Getting rid of foreach error

foreach.php

<?php
// double any value whose key starts with 'b'
$arr = array('a'=>1, 'b1'=>2, 'b2'=>3, 'c'=>4, 'd'=>5);
$non_array = null;

// Normal usage with an array
print "Test 1:\n";
foreach ($arr as $key => $val) {
    print "Key $key, Value $val\n";

}

// Normal usage with a non-array (undefined or otherwise empty data set)
// Outputs: Warning: Invalid argument supplied for foreach() in test.php on line 16
print "Test 2:\n";
foreach ($non_array as $key => $val) {
    print "Key $key, Value $val\n";
}

// By casting the $non_array to an (array) type, it will function without error, skipping the loop
print "Test 3:\n";
foreach ((array) $non_array as $key => $val) {
    print "Key $key, Value $val\n";
}

print "Done.\n";