这两个函数在php中有什么区别？

Question

These function statements are confusing me.

I'm new to php, help me to understand these functions:

function addFive($num)
{
$num += 5;
}

function addSix(&$num)
{
$num += 6;
}
$orignum = 10;
addFive( $orignum );
echo "Original Value is $orignum<br />";
addSix( $orignum );
echo "Original Value is $orignum<br />";

first echo outputs 10 Second echo outputs 16

What is the difference between these 2 functions?

Answer 1

There are two types of call:

1) Call by value: addFive($num)

2) Call by reference: addSix(&$num)

In first case, you are just passing value of the variable.

Hence, only value gets modified keeping original variable untouched.

In second case, you are passing reference to the variable, hence the original value gets modified.

Answer 2

The first function passes the argument by value - in other words, it's copied into the function, and any change you perform on it will be on the local copy.

The second function passes the argument by reference (note the & before it in the function's signature). This means the variable itself is passed, and any modification you perform on it will survive beyond the function's scope.

Answer 3

& is used to pass address of an variable in second function declaration "addSix(&$num) {}"

In second function while calling addSix( $orignum ); updation of value is done on address of "$orignum"

whereas in first function updation is done on "$num"

Answer 4

第一个函数在您的数字上加5，第二个函数在您的数字上加6 $num+=6表示$num= $num+6第一个函数在Call by value起作用，第二个函数在Call by reference起作用