php amazing question and logical answer

Question: What is output of 1...1?
Its Output is 10.1
How?
Divide it into three points.

1.

.

.1

1. 1.0 is equal to 1
2. 2nd . is a concatenation operator
3. .1 is equal to 0.1
4. So {1} {.} {0.1} is EQUAL to 10.1

Question: What is final value of $a, $b in following?

$a = '1';
$b = &$a;
$b = "2$b";
echo $a;
echo $b;

output

21
21

Explaination

$a = '1'; //1
$b = &$a; //both are equal
$b = "2$b"; //now $b=21
echo $a;  //21
echo $b; //21

Question: What is output of 016/2?
Output is : 7. The leading zero indicates an octal number in PHP, so the decimal number 14 instead to decimal 16;

echo 016; //14

echo 016/2; //7