Numeric Base
The numeric base is the number of digits to be used when counting. The most common bases are: binary 0 and 1, octal 0 to 7, decimal 0 to 9, duodecimal 0 to 11, hexadecimal 0 to F, aka 15.
All other bases, starting from 2, are possible.
In computer science, base 2, 10 and 16 are quite common, and require conversion from one another.
<?php
$number = '1234';
echo base_convert($number, 10, 8); // 2322
echo base_convert($number, 10, 12); // 86a
echo base_convert($number, 10, 16); // 4d2
?>