Value Transfer and reference transfer in PHP

 

Value Transfer and reference transfer exist in PHP. The latter must use the address operator & to identify the variable. The following is an example of assigning values:

1, Value transfer

1) Basic data types:

 
<? PHP $ A = 1; $ B = $ A; $ B + = 2; echo"\ $ A =". $ ."<Br/>"; Echo"\ $ B =". $ B ."<Br/>";/* Output: $ A = 1 $ B = 3 */?>
 

Note: The $ B = $ a statement is used to assign the value of $ A to $ B. That is, the value assigned is 1.

After the statement $ B + = 2 is executed:

Therefore, $ B is changed to 3, but the value of $ A is not changed.

2) Reference Data Type

The person class is as follows:

<?PHP class person {private $ _ name; Public Function setname ($ name) {$ this-> _ name = $ name;} public function getname () {return $ this-> _ name;} public function tostring () {return"Name is". $ This-> _ name ;}}?>
 

Initialize two person class objects and set attributes:

 

3	$ P2 = new person ();
4	$ P2-> setname ("person2 ");

Perform the following operations:

1	$ P3 = $ P1;

Test:

1	Echo "\ $ P1's". $ P1-> tostring (). ". <br/> ";
2	Echo "\ $ P3's". $ P3-> tostring (). ". <br/> ";

3
4	/* Output:

5	$ P1's name is person1.
6	$ P3's name is person1.

7

*/

 

NOTE: For the $ P3 = $ P1 statement, the value assigned is 0x000a. That is, $ P1 and $ P3 both reference the same object.

2, Reference Transmission

1) Basic Data Types

01	<? PHP
02	$ A = 1;

03	$ B = & $;
04	$ B + = 2;

05
06	Echo "\ $ A =". $ A. "<br/> ";

07	Echo "\ $ B =". $ B. "<br/> ";
08

09	/* Output:
10	$ A = 3

11	$ B = 3
12	*/

13

?>

Note: The $ B = & $ a statement is used for reference transfer. That is, the value assigned is 0x0001.

So after $ B + = 2,

Therefore, the values of $ A and $ B are both 3.

2) Reference Data Type

If you perform the following operations to replace the previous $ P3 = $ p1

1	$ P3 = & $ P1;

Then, perform the following operations:

1	$ P3 = $ P2;

The test results are as follows:

1	Echo "\ $ P1's". $ P1-> tostring (). ". <br/> ";
2	Echo "\ $ P3's". $ P3-> tostring (). ". <br/> ";

3
4	/* Output:

5	$ P1's name is person2.
6	$ P3's name is person2.

7

*/

Note: the result of $ P3 is clear, because $ P3 = $ P2 is executed, but why is the result of printing $ P1 different from the previous one?

It is because after the $ P3 = & $ P1 statement is executed, the value assigned is 0x0001.

Then run the $ P3 = $ P2 statement.

Therefore, the above result information is printed. This is the address operator.

CompleteCodeAs follows:

1) Reference Data Type

01	<? PHP
02	Class person {

03	Private $ _ name;
04

05	Public Function setname ($ name ){
06	$ This-> _ name = $ name;

07	}
08

09	Public Function getname (){
10	Return $ this-> _ name;

11	}
12

13	Public Function tostring (){
14	Return "name is". $ this-> _ name;

15	}
16	}

17
18	$ P1 = new person ();

19	$ P1-> setname ("person1 ");
20	$ P2 = new person ();

21	$ P2-> setname ("person2 ");
22

23	$ P3 = $ P1;
24	// $ P3 = & $ P1;

25	// $ P3 = $ P2;
26	Echo "\ $ P1's". $ P1-> tostring (). ". <br/> ";

27	Echo "\ $ P3's". $ P3-> tostring (). ". <br/> ";
28	?>

2) Basic Data Types

1	<? PHP
2	$ A = 1;

3	$ B = $;
4	// $ B = & $;

5	$ B + = 2;
6

7	Echo "\ $ A =". $ A. "<br/> ";
8	Echo "\ $ B =". $ B. "<br/> ";

9

?>

Conclusion: The transfer of values and references are similar to the assignment operation when the methods and function parameters are passed.