php function that Recursively converts nested array into a flat one with preserved keys connected with connector.

flatArray.php

<?php
	/**
	 * Recursively converts nested array into a flat one with keys preserving.
	 * @param array $result Resulting array
	 * @param array $array Source array
	 * @param string $prefix Key's prefix
	 * @param string $connector Levels connector
	 */
	function flatArray(array &$result, array $array, $prefix = null, $connector = '.') {
		foreach ($array as $key => $value) {
			if (is_array($value))
				flatArray($result, $value, $prefix.$key.$connector, $connector);
			else
				$result[$prefix.$key] = $value;
		}
	}

indexArray.php

<?php
	/**
	 * Reindexes array with second-level value.
	 * @param array $array Array to reindex
	 * @param stirng $field Field to use as index
	 */
	function indexArray(array &$array, $field) {
		$copy = $array;
		$array = array();
		foreach ($copy as $value) {
			$array[$value[$field]] = $value;
		}
	}

packArray.php

<?php
	/**
	 * Packs many arrays into one with keeping their indexes.
	 * @param string $indexes Array names separated by colon.
	 * @param array... Arrays to be packed.
	 * @return array Result of packing.
	 */
	function packArrays($indexes) {
		$arrays = func_get_args();
		$indexes = explode(':', array_shift($arrays));
		// first algorithm
		/*
		$packed = array();
		foreach ($arrays as $array_n => $array) {
			foreach ($array as $key => $value) {
				$packed[$key][$indexes[$array_n]] = $value;
			}
		}
		krsort($packed);
		*/
		// second algorithm
		#/*
		$keys = array();
		foreach ($arrays as $array) $keys = array_merge($keys, array_keys($array));
		$keys = array_unique($keys);
		if (empty($keys)) return array();
		rsort($keys);
		$packed = array_combine($keys, array_fill(0, count($keys), array()));
		foreach ($arrays as $array_n => $array) {
			foreach ($array as $key => $value) {
				$packed[$key][$indexes[$array_n]] = $value;
			}
		}
		#*/
		return $packed;
	}