为什么它是0而不是255？

Question

echo intval(chr(255));

I don't understand...

Answer 1

The chr() function turns a byte into its ASCII equivalent and intval() function gets the integer value of a variable.

If we were to break the statement into two different lines, this would be:

$a = chr(255); // $a is now a string
echo intval($a);

If you check intval()'s documentation you will notice that:

Strings will most likely return 0 although this depends on the leftmost characters of the string. The common rules of integer casting apply.

That's why the result is zero.