array_to_sentence.php

<?php
function array_to_sentence($arr)
{
	$s = "";
	if (count($arr) === 1) {
		$s = $arr[0];
	} elseif (count($arr) === 2) {
		$s = $arr[0] . " and " . $arr[1];
	} else {
		$slice = array_slice($arr, 0, count($arr) - 1);
		$last = $arr[count($arr) - 1];
		$s = join(", ", $slice) . ", and " . $last;
	}
	return $s;
}