<?php

/**
 * Callback function for preg_replace_callback
 * Randomly return one word in list
 * 
 * @param	Array	$match	matched result from preg_replace_callback pattern
 * @return	String		random word in list
 */
function spin_replace_callback($match)
{
	$words = explode('|', $match[1]);
	return $words[array_rand($words)];
}

/**
 * Process each spin block in string
 * 
 * each block must start with "{" and end with "}"
 * separate each word with "|"
 *
 * eg. {hello|hi} {everyone|everybody}
 * 
 * @param	String	$text	string to process spin text block
 * @return	String		spin result
 */
function process_spin_block($text)
{
	return preg_replace_callback('~\{(.*?)\}~', 'spin_replace_callback', $text);
}

วิธีใช้

<?php
echo process_spin_block('{Hello|Hi} {everyone|everybody}. Do you know {who|what} am i ?');