Literal Types

Edit pageLast modified: 02 February 2025

As a type description, specific values corresponding to a specific type are allowed:

  • bool

  • string

  • int

  • float

  • null.

Boolean And Null

The literals true and false are used as the value of the PHP bool type.

tip

Note: true and false values are not case sensitive.

TruE

For PHP null types, the null literal is used.

tip

Note: null value is not case sensitive.

NulL

For other types the logic is more complicated.

Strings

The syntax of string types is similar to that in PHP: The string allows single (') and double (") quotes, which can be escaped using a backslash (\).

tip

Single-quoted string wrapped by ' symbol.

'I am single-quoted string wrapped by \' symbol'

tip

Double-quoted string wrapped by " symbol.

"I am double-quoted string wrapped by \" symbol"'

Strings in single quotes are processed "as is", strings in double quotes allow insertion of special sequences.

Escape Sequences

All control sequences are similar to the PHP language: https://www.php.net/manual/en/language.types.string.php

  • \n — Line break (0x0A code)

  • \r — Carriage return (0x0D code)

  • \t — Tab (0x09 code)

  • \v — Vertical Tab (0x0B code)

  • \e — Escape (0x1B code)

  • \f — Form Feed (0x0C code)

  • \$ — Dollar Sign (0x24 code)

tip

Double-quoted string with new line (0x0A) escape sequence.

"String with\nNew Line"
String with
New Line

tip

Single-quoted string with ignored escape sequence.

'String without\nNew Line'
String without\nNew Line

Hexadecimal Sequences

The sequence of characters matching the regular expression [0-9A-Fa-f]{1,2} is a character in hexadecimal notation (e.g. "\x41" === "A").

tip

"Hello World" string equivalent in hexadecimal sequences format.

"\x48\x65\x6c\x6c\x6f\x20\x57\x6f\x72\x6c\x64"
Hello World

tip

Single-quoted string does not process such sequences.

'\x48\x65\x6c\x6c\x6f\x20\x57\x6f\x72\x6c\x64'
\x48\x65\x6c\x6c\x6f\x20\x57\x6f\x72\x6c\x64

Unicode Sequences

the sequence of characters matching the regular expression [0-9A-Fa-f]+ is a Unicode codepoint, which will be output to the string as that codepoint's UTF-8 representation. The braces are required in the sequence. E.g. "\u{41}" === "A"

tip

"😊" unciode char equivalent.

"\u{1F60A}"
😊

tip

Single-quoted string does not process such sequences.

'\u{1F60A}'
\u{1F60A}

Integer

The syntax of integer numbers is similar to the PHP language. Binary, octal, decimal and hexadecimal number systems are supported.

note

Please note that in addition to numbers, underscores (_) are allowed.

Decimal numbers can contain any digits from 0 to 9 (leading 0 not allowed) and must match the regular expression [1-9][0-9]*. For any other numbers, a special prefixed format is used, described below. Negative values are prefixed with a minus (-).

Binary

Every binary number is prefixed with 0b or 0B and can only contain the numbers 1 and 0 and must match the regular expression 0b[0-1]+.

tip

Number 173 in binary format.

0b10101101

tip

Also number 173 in binary format with _ delimiters.

0b10_10_11_01

tip

Number 10 in binary format:

  • The 0b or 0B prefix can be in any case.

0B1010

tip

Negative number 10 in binary format.

-0b1010

Octal

Every octal number is prefixed with 0o or 0O and can only contain the numbers between 0 and 7 and must match the regular expression 0o[0-7]+ or [0-7]+.

note

For compatibility with older versions of PHP, the prefix 0 is also allowed.

tip

Number 34 in octal format.

0o42

tip

Also number 34 in octal format:

  • The 0o or 0O prefix can be in any case.

0O42

tip

Also number 34 in "legacy" octal format.

042

tip

Number 2195 in octal format with _ delimiters.

0o42_23

Hexadecimal

Every hexadecimal number is prefixed with 0x or 0X and can only contain the numbers between 0 and F and must match the regular expression 0x[0-9a-fA-F]+.

tip

Number 57005 in hexadecimal format.

0xDEAD

tip

Also number 57005 in hexadecimal format:

  • The 0x or 0X prefix can be in any case.

  • The A-F letters can also be in any case.

0XDeaD

tip

Number 3735928559 in hexadecimal format with _ delimiters.

0xDEAD_BEEF

Float

The syntax of float numbers is similar to the PHP language. Basic floating point syntax and scientific notation are supported.

Every floating point number accepts the format [0-9]+\.[0-9]+. The leading or trailing number may be omitted. Negative values are prefixed with a minus (-.

tip

Simple floating point literal value.

0.9

tip

Non-prefixed floating point literal value (equivalent of 0.9).

.9

tip

Non-suffixed floating point literal value (equivalent of 1.0).

1.

tip

Negative floating point literal value.

-0.9

Scientific Notation

Scientific notation is a way of expressing numbers that are too large or too small to be conveniently written in decimal form, since to do so would require writing out an inconveniently long string of digits.

tip

Number 1000.0 in scientific notation.

10e2

tip

Also number 1000.0 in scientific notation:

  • The e or E suffix can be in any case.

10E2

tip

Number 0.1 in scientific notation (negative exponent).

10e-2