PHP technique without the third variable swap two variable value solution

Text (explanation see code comment)

I, substr () && strlen ()

Code:

<?php/** * When a variable is a string, the available Exchange method one * uses substr () combined with strlen () two methods to achieve the exchange variable worth the purpose */$a = "This is a"; A variable original value $b = "this is B"; b Variable original value echo ' Exchange before $a value: '. $a. ', $b value: '. $b, ' <br> '; Output original Value $ A. = $b; Append the value of $b to $ A/** * $b get a $ A value in detail: * The      length of the string in $ A and $b is calculated first by strlen () respectively "At this time $ A is the value of the original $ A and $b" *      through strlen ($a)-strlen ($b) You can get the value length of the original $ A *      in the merged $ A by substr () method from 0 to the length of a $ A, then you can obtain the original $ A value * $a get the $b value in detail: *      because the $b is already a $ A original value, and $ A combined value of the original $ A + original $b value, so the substr () in $ A from the $b (original $ A) length position interception, the content is the original $b, then the $b value to $ A success  /$b = substr ($a, 0, (strlen ($a)-strlen ($b)); A  = substr ($a, strlen ($b)); $a value after Echo ' Interchange: '. $a. ', $b value: '. $b, ' <br> ';//output result value

Operation Result:

Value $a before swapping: this is a, $b value: this is b
Value after Exchange $a: This is B, the value of $b: This is a

Second, Str_replace ()

Code:

<?php/** * When both variables are strings, the available Exchange Method II * uses the Str_replace () method to achieve the swap variable worth the purpose * This method is slightly simpler than the first one, a little more logically */$a = "This is a"; A variable original value $b = "this is B"; b Variable original value echo ' Exchange before $a value: '. $a. ', $b value: '. $b, ' <br> '; Output original Value $ A. = $b; Append the value of $b to $ A $b  = Str_replace ($b, "", $a); In $ A (original $a+ $b), replace $b with empty, then the remaining return value is $a$a  = Str_replace ($b, "", $a); At this point, the $b is the original $ A value, and the $b (original $ A) is replaced with a null in $ A (original $a+ $b), the remaining return value is the original $b, the value of the exchange succeeds after the Echo ' Interchange $a: '. $a. ', $b value: '. $b, ' <br> '; Output result value

Operation Result:

Value $a before swapping: this is a, $b value: this is b
Value after Exchange $a: This is B, the value of $b: This is a

Iii. list () && list ()

Code:

<?php/** * When a variable is a string, the Exchange method can be used three * using the list () and array () methods to achieve the exchange variable worth the purpose * This method is the first to second, the code is the most concise */$a = "This is a"; A variable original value $b = "this is B"; b Variable original value echo ' Exchange before $a value: '. $a. ', $b value: '. $b, ' <br> '; Output raw Value list ($b, $a) = Array ($a, $b); The list () function assigns values to a set of variables using the elements in the array. Know this, believe the others don't have to say it. Echo ' Exchange $a value after: '. $a. ', $b value: '. $b, ' <br> '; Output result value

Operation Result:

Value $a before swapping: this is a, $b value: this is b
Value after Exchange $a: This is B, the value of $b: This is a

Iv.. Xor or

Code:

<?php/** * When a variable is a string or a number, the available method of Exchange four * uses the XOR operation */$a = "This is a"; A variable original value $b = "this is B"; b Variable original value echo ' Exchange before $a value: '. $a. ', $b value: '. $b, ' <br> '; Output Original Value/** * Original binary: * $a: 010101000110100001101001011100110010000001101001011100110010000001000001 * $b: 0 10101000110100001101001011100110010000001101001011100110010000001000010 *  * The following are mainly used in the bitwise XOR or exchange, please refer to the following binary procedure, */$ A= $a ^ $b; At this moment $a:000000000000000000000000000000000000000000000000000000000000000000000011$b= $b ^ $a; At this moment $b:010101000110100001101001011100110010000001101001011100110010000001000001$a= $a ^ $b; At this moment $a:010101000110100001101001011100110010000001101001011100110010000001000010echo ' Exchange $a value: '. $a. ', $b value: '. $b, ' <br> '; Output result value

Operation Result:

Value $a before swapping: this is a, $b value: this is b
Value after Exchange $a: This is B, the value of $b: This is a

Five, plus (+) minus (-) operators

Code:

<?php/** * When the two variables are numeric, the available Exchange method is five * using the Add and subtract operator, which is equivalent to the mathematical operation of ^_^ */$a = "This is a"; A variable original value $b = "this is B"; b Variable original value echo ' Exchange before $a value: '. $a. ', $b value: '. $b, ' <br> '; Output original value $a= $a + $b; $a $b and value $b= $a-$b; Not explained. $a = $a-$b; Not explained. Echo ' Exchange $a after the value: '. $a. ', $b value: '. $b, ' <br> '; Output result value

Operation Result:

Value $a before swapping: 1,

$b value: 2 after Exchange

$a value: 2, $b value: 1

Summarize

OK, the above is almost all the methods in PHP without the use of the third variable to exchange two variable values, of course, there must be better, I am here to be a point.

In the final analysis, all are small algorithms, we can also study under the time.

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