Add rules for operand in pre/post-inc/decrement

[Majkl578]

Type check for int/float in:

• $foo++
• $foo--
• ++$foo
• --$foo

Note that PHP allows wide range of scary and inconsistent magic in these operators which I do not want to implement; some examples:

php > $x = false;
php > $x++;
php > var_dump($x);
bool(false)

php > $x = 'xx';
php > $x++;
php > var_dump($x);
string(2) "xy"

php > $x--;
php > var_dump($x);
string(2) "xy"

php > $x = '?';
php > $x++;
php > var_dump($x);
string(1) "?"

php > $x = 'x2';
php > $x++;
php > var_dump($x);
string(2) "x3"
php > $x = 'x7';
php > $x++;
php > $x++;
php > $x++;
php > var_dump($x);
string(2) "y0"

php > $x = 'zz';
php > $x++;
php > var_dump($x);
string(3) "aaa"

php > $x = ';z9';
php > $x++;
php > $x++;
php > $x++;
php > var_dump($x);
string(3) ";a2"

[ondrejmirtes]

Thanks! 👍