Hexadecimal Separator

<?php

echo 123_456;
echo 12.45_56;
echo 0x12_34;
echo 0b111_110_001;
echo 0b111_110_00_1;

echo mb_chr(0x1F_418); // OK
echo "\u{1F4_18}";   // KO

?>

PHP offers a number separator since PHP 8.0: _. It may be added inside any integer or float, to make long list of digits more readable.

In fact, this also applies to the other integer notations: hexadecimal, octal, binary, etc. Just don’t put it inside the header, like 0_x_1, but in the body of the integer.

Interestingly, the separator does not work in string sequences, like inside an hexadecimal unicode representation.

See Also

• Hexadecimal separated [Try me]

PHP Error Messages

• Invalid UTF-8 codepoint escape

PHP Features

• numeric-separator
• underscore
• hexadecimal-integer
• octal-integer
• binary-integer
• unicode
• escape-sequence

Last updated: 10 September 2026