The difference between php reference and copy

Regarding value passing and reference passing, the explanations in books are relatively cumbersome, but they always appear in PHP interviews. Below, I will use a life example to help you understand the difference between them.

Step 1

Suppose we go to a hotel to book a room. We compare the hotel's house number to a variable name, and we use the number of people in the room as the variable name. The process of assignment

<?php
$k1=2;//$k1号房间住了2个人
$k2=$k1;//恰巧今天$k1号房间维修，把$k1号房间的人放到$k2房间里面
$k1=10；//假设$k1维修好了，又住进10个人，那么这就是值传递。
echo  "$k1号房间:".$k1."个人"；//10
echo  "$k2号房间:".$k2."个人"；//1
?>

Characteristics of value transfer:

1. Value equality

That is, $k1 to $k2 The people in the room are equal.

2. Mutual independence and no influence on each other

That is to say, the number of guests in my $k1 room and the number of guests in my $k2 room do not affect each other. . This is called: "Different ways do not work together."

Second step

Take the above example and assume that our room $k1 is hung up by the maintenance worker with two house numbers $k1 and $k2 to understand

<?php
$k1=2;//$k1号房间住了2个人
$k2=&$k1;//恰巧今天$k1号房间挂上"$k1"和“$k2”两个门牌号
$k1=10；//假设$k1又住进10个人，那么这就是引用传递。
echo  "$k1号房间:".$k1."个人"；//10
echo  "$k2号房间:".$k2."个人"；//10因为门牌$k1房间的客人就是门牌$k2里面的客人
?>

Characteristics of reference passing:

mutual influence, that is to say, how many guests come in $k1, and how many guests are displayed in $k2, which is called "tied on a rope" The grasshopper".

Difference

1. Difference in usage

The symbol passed by the value is =

quote The transfer symbol is &

2. The difference in meaning

Value transfer means that variables are transferred without affecting each other, while reference transfer means that two variables point to the same space. influencing each other.

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