How to swap the values ​​of two variables in PHP (without using a third variable)

Preface

Today we will take a look at how to achieve the purpose of exchanging two variables in PHP without using a third variable. See the code comments for detailed explanation, let’s take a look below.

1. substr() && strlen()

Code:

<?php
/**
 * 双方变量为字符串时，可用交换方法一
 * 使用substr()结合strlen（）两个方法达到交换变量值得目的
 */
$a = "This is A"; // a变量原始值
$b = "This is B"; // b变量原始值
echo &#39;交换之前 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出原始值
$a .= $b; // 将$b的值追加到$a中
/**
 * $b得到$a值详解：
 *  先通过strlen()分别计算出$a和$b中字符串的长度【此时$a是原始$a和$b的合值】
 *  通过strlen($a)-strlen($b)即可得出原始$a的值长度
 *  在通过substr()方法在合并后的$a中从0开始截取到$a的长度，那么即可得到原始$a的值
 * $a得到$b值详解：
 *  由于此刻$b已经是$a的原始值了，而$a合并后的值为原始$a+原始$b的值，故用substr()在$a中从$b(原始$a)长度位置截取，则去的内容则为原始$b，则将$b值付给$a成功
 */
$b = substr($a,0,(strlen($a)-strlen($b)));
$a = substr($a, strlen($b));
echo &#39;交换之后 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出结果值

Run result:

The value of $a before the exchange: This is A, the value of $b: This is B

The value of $a after the exchange: This is B, value of $b: This is A

2. str_replace()

Code:

<?php
/**
 * 双方变量为字符串时，可用交换方法二
 * 使用str_replace()方法达到交换变量值得目的
 * 此方法较第一种，逻辑上稍微简单点
 */
$a = "This is A"; // a变量原始值
$b = "This is B"; // b变量原始值
echo &#39;交换之前 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出原始值
$a .= $b; // 将$b的值追加到$a中
$b = str_replace($b, "", $a); // 在$a(原始$a+$b)中，将$b替换为空，则余下的返回值为$a
$a = str_replace($b, "", $a); // 此时，$b为原始$a值，则在$a(原始$a+$b)中将$b(原始$a)替换为空，则余下的返回值则为原始$b,交换成功
echo &#39;交换之后 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出结果值

Run result:

The value of $a before exchange: This is A, the value of $b: This is B

After exchange, the value of $a: This is B, the value of $b: This is A

3. list() && list()

Code:

<?php
/**
 * 双方变量为字符串时，可用交换方法三
 * 使用list()和array()方法达到交换变量值得目的
 * 此方法较第一、二种，代码最简洁
 */
$a = "This is A"; // a变量原始值
$b = "This is B"; // b变量原始值
echo &#39;交换之前 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出原始值
list($b,$a) = array($a,$b); // list() 函数用数组中的元素为一组变量赋值。了解这个，相信其他的不用我多说了吧
echo &#39;交换之后 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出结果值

Run result:

Value of $a before exchange: This is A, $b Value of: This is B

Value of $a after exchange: This is B, Value of $b: This is A

4. Exclusive OR

Code:

<?php
/**
 * 双方变量为字符串或者数字时，可用交换方法四
 * 使用异或运算
 */
$a = "This is A"; // a变量原始值
$b = "This is B"; // b变量原始值
echo &#39;交换之前 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出原始值
/**
 * 原始二进制：
 * $a:010101000110100001101001011100110010000001101001011100110010000001000001
 * $b:010101000110100001101001011100110010000001101001011100110010000001000010
 * 
 * 下面主要使用按位异或交换，具体请参照下列给出的二进制过程，
 */
$a=$a^$b; // 此刻$a:000000000000000000000000000000000000000000000000000000000000000000000011
$b=$b^$a; // 此刻$b:010101000110100001101001011100110010000001101001011100110010000001000001
$a=$a^$b; // 此刻$a:010101000110100001101001011100110010000001101001011100110010000001000010
echo &#39;交换之后 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出结果值

Running result:

Value of $a before exchange: This is A, the value of $b: This is B

The value of $a after exchange: This is B, the value of $b: This is A

5. Add (+) Subtraction (-) operator

Code:

<?php
/**
 * 双方变量为数字时，可用交换方法五
 * 使用加减运算符，相当于数学运算了^_^
 */
$a = "This is A"; // a变量原始值
$b = "This is B"; // b变量原始值
echo &#39;交换之前 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出原始值
$a=$a+$b; // $a $b和值
$b=$a-$b; // 不解释..
$a=$a-$b; // 不解释..
echo &#39;交换之后 $a 的值：&#39;.$a.&#39;, $b 的值：&#39;.$b,&#39;<br>&#39;; // 输出结果值

Running result:

The value of $a before the exchange: 1, the value of $b: 2

The value of $a after the exchange: 2, the value of $b: 1

Summary

Okay, the above is almost all the ways to exchange the values ​​​​of two variables in PHP without using a third variable. Of course, there must be a better way. I am here to introduce some ideas. . After all, they are all small algorithms, and you can study them yourself when you have time. I hope the content of this article can be of some help to everyone's study or work. If you have any questions, you can leave a message to communicate. Thank you all for your support of Script House.

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