PHP: Generate all possible alphabetical combinations of given strings

string_combination_generator.php

/**
 * Generate all possible alphabetical combinations of given strings
 *
 * @param array $strings - Strings to combine
 * @param array $combinationArray - for internal use only
 * @param int $start - for internal use only
 * @param string $prefix - for internal use only
 * @return array
 */
function generateCombinations($strings, &$combinationArray = array(), $start = 0, $prefix = "")
{
    for ($i = $start; $i < count($strings); $i++) {
        $combination = $prefix . $strings[$i];
        $combinationArray[] = $combination;
        $this->generateCombinations($strings, $combinationArray, ++$start, $combination);
    }
    return $combinationArray;
}