自訂levenshtein 目的：了解levenshtein 演算法原理

参考 ： http://www.cnblogs.com/ymind/archive/2012/03/27/fast-memory-efficient-Levenshtein-algorithm.html

function _levenshtein($src, $dst){
	if (empty($src)) {
		return $dst;
	}
	if (empty($dst)) {
		return $src;
	}

	$temp = array();

	for($i = 0; $i <= strlen($src); $i++) {
		$temp[$i][0] = $i;
	}
	for($j = 0; $j <= strlen($dst); $j++) {
		$temp[0][$j] = $j;
	}
	for ($i = 1;$i <= strlen($src); $i++) {

		$src_i = $src{$i - 1};

		for ($j = 1; $j <= strlen($dst); $j++) {

			$dst_j = $dst{$j - 1};

			if ($src_i == $dst_j) {
				$cost = 0;
			} else {
				$cost = 1;
			}
			$temp[$i][$j] = min($temp[$i-1][$j]+1, $temp[$i][$j-1]+1, $temp[$i-1][$j-1] + $cost);
		}

	}
    return $temp[$i-1][$j-1];
}

echo _levenshtein("hello", "HElloo");