PHP does not use a third variable to exchange the values ​​​​of two variables_PHP tutorial

I once did a php interview question like this: Exchange the values ​​of two variables without using a third variable. Generally, a third intermediate variable is used to exchange the values ​​of the original two variables, but this question requires that the intermediate variable cannot be used, which is also a difficult problem for beginners. Several methods found on the Internet are summarized as follows:

<span //</span><span 字符串版本 结合使用substr，strlen两个方法实现</span>
<span $a</span>="a"<span ;
</span><span $b</span>="b"<span ;
</span><span echo</span> '交换前 $a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
</span><span $a</span>.=<span $b</span><span ;
</span><span $b</span>=<span substr</span>(<span $a</span>,0,(<span strlen</span>(<span $a</span>)-<span strlen</span>(<span $b</span><span )));
</span><span $a</span>=<span substr</span>(<span $a</span>, <span strlen</span>(<span $b</span><span ));
</span><span echo</span> '交换后$a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
 
</span><span echo</span> '-----------------------<br/>'<span ;
 
</span><span //</span><span 字符串版本 使用str_replace方法实现</span>
<span $a</span>="a"<span ;
</span><span $b</span>="b"<span ;
</span><span echo</span> '交换前 $a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
</span><span $a</span>.=<span $b</span><span ;
</span><span $b</span>=<span str_replace</span>(<span $b</span>, "", <span $a</span><span );
</span><span $a</span>=<span str_replace</span>(<span $b</span>, "", <span $a</span><span );
</span><span echo</span> '交换后$a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
 
</span><span echo</span> '-----------------------<br/>'<span ;
 
</span><span //</span><span 字符串版本 结合使用list方法和array实现</span>
<span $a</span>="a"<span ;
</span><span $b</span>="b"<span ;
</span><span echo</span> '交换前 $a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
</span><span list</span>(<span $b</span>,<span $a</span>)=<span array</span>(<span $a</span>,<span $b</span><span );
</span><span echo</span> '交换后$a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
 
</span><span echo</span> '-----------------------<br/>'<span ;
 
</span><span //</span><span 字符串和数字都适用 使用异或运算</span>
<span $a</span>='a'<span ;
</span><span $b</span>='b'<span ;
</span><span echo</span> '交换前 $a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
</span><span $a</span>=<span $a</span>^<span $b</span><span ;
</span><span $b</span>=<span $b</span>^<span $a</span><span ;
</span><span $a</span>=<span $a</span>^<span $b</span><span ;
</span><span echo</span> '交换后$a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
 
</span><span echo</span> '-----------------------<br/>'<span ;
 
</span><span //</span><span 只适用于数字</span>
<span $a</span>=3<span ;
</span><span $b</span>=5<span ;
</span><span echo</span> '交换前 $a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />'<span ;
</span><span $a</span>=<span $a</span>+<span $b</span><span ;
</span><span $b</span>=<span $a</span>-<span $b</span><span ;
</span><span $a</span>=<span $a</span>-<span $b</span><span ;
</span><span echo</span> '交换后$a:'.<span $a</span>.',$b:'.<span $b</span>.'<br />';

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