Number with 0 on the front? [closed]

Answer 1

Numbers with zero are octal numbers. So 012 is an octal number.

From the PHP manual:

$a = 0123; // octal number (equivalent to 83 decimal)

Answer 2

Numbers prefixed with 0 are treated as octal numbers:

$x = 012;//$x is 10

Details here

The reason that $x = '012'; works is because PHP converts that to an integer without treating it as an octal number.