The example.php file:

<?php

/**
 * A simple function that multiply two int or float and return a float number.
 * It throws an exception if arguments given have a wrong type.
 *
 * <code>
 *
 * printf("%01.2f\n", multiply(3, 4));
 * printf("%01.2f\n", multiply(3.2, 4));
 * printf("%01.2f\n", multiply(3.2, 4.2));
 * try {
 *     multiply('foo', 4.2);
 * } catch (Exception $exc) {
 *     echo $exc->getMessage() . "\n";
 * }
 * try {
 *     multiply(3.2, 'foo');
 * } catch (Exception $exc) {
 *     echo $exc->getMessage() . "\n";
 * }
 * // expects:
 * // 12.00
 * // 12.80
 * // 13.44
 * // Wrong type for first argument.
 * // Wrong type for second argument.
 *
 * </code>
 *
 * @param mixed $a an int or a float
 * @param mixed $b an int or a float
 *
 * @return float the result of the multiplication
 * @throws Exception if arguments given have a wrong type
 */
function multiply($a, $b)
{
    // check first arg type
    if (!is_int($a) && !is_float($a)) {
        throw new Exception("Wrong type for first argument.");
    }
    // check second arg type
    if (!is_int($b) && !is_float($b)) {
        throw new Exception("Wrong type for second argument.");
    }
    return (float)($a * $b);
}

?>

And to run the tests in this example file:

$ phpdt example.php
[PASS] function multiply in file "/home/izi/example.php"

Total time    : 0.0446 sec.
Passed tests  : 1
Skipped tests : 0
Failed tests  : 0