Leading Zero Means Octal

PHP integer syntax has some special formats for binary, octal and hexadecimal formats. In particular, an integer starting with 0 is in octal format. This leads to easy confusion, as the leading 0 is considered neutral.

In PHP 8.0, a new notation with an 0 was introduced: it makes the octal format just as explicit as the binary or the hexadecimal one.

Octals are mainly used with the mkdir() function, and special math domains.

<?php

echo 017; // displays 15
echo 0o17; // displays 15

echo 17; // displays 17

echo 0x17; // displays 23 (hexadecimal format)

?>

Documentation

See also https://php.watch/versions/8.1/explicit-octal-notation

Added in PHP 8.1