PHP只支持10,8,16进制：

Integer s can be specified in decimal (base 10), hexadecimal (base 16), or octal (base 8) notation, optionally preceded by a sign (- or +).

To use octal notation, precede the number with a 0 (zero). To use hexadecimal notation precede the number with 0x.

但是可以试用bindec():

echo bindec('110011'); 

输出

51