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

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2020-01-02 17:29:384296browse

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. 】

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<?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!

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