Retry function for PHP with linear backoff

retry.php

<?php

/* 
 * Retry function for e.g. external API calls
 *
 * Will try the risky API call, and retries with an ever increasing delay if it fails
 * Throws the latest error if $maxRetries is reached,
 * otherwise it will return the value returned from the closure.
 *
 */

function retry(callable $callable, $args = NULL, $maxRetries = 20, $initialWait = 1.0, $additionalWait = 1)
{
    try {
        return call_user_func($callable, $args);
    } catch (Exception $e) {
        // get whole inheritance chain
        $errors = class_parents($e);
        array_push($errors, get_class($e));

        // linearly increasing backoff
        if ($maxRetries > 0) {
            usleep($initialWait * 1E6);
            return retry($callable, $args, $maxRetries - 1, $initialWait + $additionalWait);
        }

        // max retries reached
        throw $e;
    }
}

usage.php

<?php

# var used to keep track of attempts, just for this example, so we can fail a few times before succeeding.
# The retry function tracks attempts on its own.
$iter = 0;

function failtwice($input) {
        global $iter;
        $iter++;
        print("function failtwice called. input: " . $input . "\n");
        if ($iter <= 2) {
            throw new Exception('Fail twice exception. input: ' . $input);
        }
        return $iter;
}



$input_global = 'abcdef';

# normal, where it succeeds after a retry
$val = retry('failtwice', $input_global);
print("return value: " . $val . "\n");


# reset
$iter = 0;

print("this one should generate an exception")
# where it fails out after exceeding $maxRetries
$val2 = retry('failtwice', $input_global, $maxRetries = 1);



print("done\n");