A retry function for PHP.

test.retry.php

<?php
require_once dirname(__FILE__) . '/../lib/simpletest/autorun.php';

// Retries $f (A function) with arguments ($args as array)
// 3 ($retries) times after 10 secs $delay
// Usage: 
//   retry( 'function_name', array('arg1', 'arg2'), 15, 5 );
//   #=> Retries function_name 5 times with arg1 and $arg2 as arguments at interval of 15 secs 
function retry($f, $args = null, $delay = 10, $retries = 3)
{
    try {
        if ( is_null( $args ) )
            return $f();
        if ( is_array( $args ) )
            return call_user_func_array( $f, $args )
        return call_user_func_array( $f, array( $args ) );
    } catch ( Exception $e ) {
        if ( $retries > 0 ) {
            sleep( $delay );
            return retry( $f, $delay, $retries - 1 );
        } else {
            throw $e;
        }
    }
}

class RetryTest extends UnitTestCase
{
    function testRetryWithNoExceptions()
    {
        $name = "Bob";
        $result = retry(
            function () use ($name) {
                return $name . "!";
            },
            0.1
        );

        $this->assertEqual("Bob!", $result);
    }

    function testRetryWithException()
    {
        $fail = true;
        $result = retry(
            function () use (&$fail) {
                if ($fail) {
                    $fail = false;
                    throw new Exception("Boom!");
                } else {
                    return "Woo!";
                }
            },
            0.1
        );

        $this->assertEqual("Woo!", $result);
    }

    function testRetryTriesTheExpectedNumberOfTimes()
    {
        $count = 0;
        try {
            retry(
                function () use (&$count) {
                    $count += 1;
                    throw new Exception("Boom!");
                },
                0.1
            );
        } catch (Exception $e) {
        }

        $this->assertEqual(4, $count);
    }

    function testRetryWithConstantFailure()
    {
        $this->expectException(new PatternExpectation("/I will never work./"));
        $result = retry(
            function () {
                throw new Exception("I will never work.");
            },
            0.1
        );
    }
}