PHP Address Characters &

I have a very strange problem today.

$arr =[' A ', ' B ', ' C '];foreach ($arr as & $v) {}foreach ($arr as $v) {}var_dump ($arr); unset ($v); Var_dump ($arr);

This code believes that I can see that the output is ABC

But the result is:

Array (size=3) 0 = String ' a ' (length=1) 1 = = String ' B ' (length=1) 2 = &string ' B ' (length=1) array (siz e=3) 0 = String ' a ' (length=1) 1 = = String ' B ' (length=1) 2 = String ' B ' (length=1) focuses on

2 = &string ' B ' (length=1) This place is equivalent to $v assigned to $ARR[2]

The reason for this is that the &php address character

Let's take a look at the basic usage of &:

$b = $c = 1; $a = & $b; $a = 2;echo "b= $b, c= $c \ n"; $a = & $c; $a = n, $a = 200;echo "b= $b, c= $c \ n"; unset ($a); $a = 500;ec Ho "b= $b, c= $c \ n"; After a $ A is specified as a $b reference, unless you specify another reference again, or unset ($a), changing $ A will change the value of the corresponding $b.

For you this foreach, is the same truth, you take the loop apart, this is the way:

$v = & $arr [0]; $v = & $arr [1]; $v = & $arr [2];

The loop runs to the last time, $v is a reference to $arr[2], so it is equivalent to this form:

$arr [0] = A; $arr [1] = b; $v = & $arr [2]; $arr [2] = B;var_dump ($arr);

It is not difficult to understand why Var_dump will print a & symbol on the last key-value pair.

PHP address character &