What is the difference between passing by value and passing by reference in php

php value transfer: within the scope of the function, changing the size of the variable value will not affect the variable value outside the function.

PHP pass-by-reference: Within the function scope, any changes to the value are also reflected outside the function, because the pass-by-reference passes the memory address.

Passing value: It is the same as copy. [For example, I have a house. I give you building materials. You build a house that is exactly the same as mine. Whatever you do in your house will not affect me. What I do in my house will not affect me. Nothing will affect you, independent of each other. 】

(Free video tutorial sharing: php video tutorial)

<?php  
$testa=1;        //定义变量a 
$testb=2;        //定义变量b  
$testb = $testa;    //变量a赋值给变量b  
echo $testb;      //显示为1  
?>

Passing reference: It is similar to the pointer of C language, and it feels almost the same. For example, I have a house. If I give you a key, both of us can enter the house. Whatever you do in the house will affect me.

<?php  
$param2=1;        //定义变量2  
$param1 = &$param2;   //将变量2的引用传给变量1  
echo $param2;      //显示为1  
$param1 = 2;       //把2赋值给变量1  
echo $param2;      //显示为2  
?>

[Advantages and Disadvantages:] Passing values ​​will be time-consuming, especially for large strings and objects. This will be a very expensive operation, transferring references, and any operation within the function. Equivalent to the operation of transferring variables, it is efficient when transferring large variables!

Recommended related articles and tutorials: php tutorial

The above is the detailed content of What is the difference between passing by value and passing by reference in php. For more information, please follow other related articles on the PHP Chinese website!