<?php
	
	$a = 'a';
	$b = 'b';
	//第一种方法 字符串截取
	$a .= $b;
	$b = substr($a,0,strlen($a)-strlen($b));
	$a = substr($a,strlen($a)-strlen($b));

	echo $a;
	echo "<br>";
	echo $b;
	echo "<br>";

	//第二种方法 字符串替换
	$a .=$b;
	$b = str_replace($b,"",$a);
	$a = str_replace($b,"",$a);
	echo $a;
	echo "<br>";
	echo $b;
	echo "<br>";

	//第三种方法 数组转换
	list($b,$a) = array($a,$b);
	echo $a;
	echo "<br>";
	echo $b;
	echo "<br>";

	//第四种方法 异或运算
	$a=$a^$b;
	$b=$b^$a;
	$a=$a^$b;
	echo $a;
	echo "<br>";
	echo $b;