The difference between a value in PHP and a pass-through reference

This article mainly introduces the invocation of PHP in the difference between the value and the reference, has a certain reference value, now share to everyone, the need for friends can refer to

PHP Transfer Value : Within the scope of the function, changing the value of a variable is not likely to affect the values of the variables outside the function.
PHP by reference : Within the scope of the function, any change to the value is also reflected outside the function, because the pass-through refers to the memory address.

Daniel's Explanation:

Pass value : Same as copy. "For example, I have a Yikanghuayuan house, I give you building materials, you built a root of my house the same house, you do nothing in your house will affect me, I do in my house do not affect you, independent of each other." "

[PHP] view plain copy

1. <?php      $testa =1;               Define variable a $testb =2;               Define variable b    $testb = $testa;       Variable a assigns a value to the variable B    echo $testb;            Display as 1    ?>

reference : similar to the C language of the pointer, feel the same. For example, I have a Yikanghuayuan house, I give you a key, two of us can enter this House, what you do in the House will affect me.

[PHP] view plain copy

1. <?php      $param 2=1;               Define variables 2    $param 1 = & $param 2;      Pass a reference to variable 2 to the variable 1    echo $param 2;            Shown as 1    $param 1 = 2;             Assign 2 to the variable 1    echo $param 2;            Display as 2    ?>

"Pros and Cons:" It takes time to pass a value, especially for large strings and objects, which can be a costly operation, delivering a reference, and any operation within a function is equivalent to the operation of a transfer variable, and high efficiency when transferring large variables!

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