Escape Sequences

Escape sequences are sequences of characters with a special meaning. Most of the time, the literal value of the character displayed is its meaning, while, sometimes, there are other hidden meaning.

An escape sequence is dedicated to a technology, and they are rare the same between two technologies, or even, between two engines dedicated to that technology.

Here are some examples of escape sequences from PHP:

  • \n: new line

  • \t: horizontal tabulation

  • "\"": double quote, inside a double quoted-string

  • \' This is not an escape sequence: single quoted string do not recognize this

  • \u{01f418}: a unicode codepoint, representing an elephpant

  • \200: a character in octal notation

  • \x69: a character in hexadecimal notation

Here are some examples of escape sequences from HTML:

  • ´ (a acute accent)

  • &quote; (double quote)

  • There are many more of them. See external links.

Escape sequences should not be confused with escape characters, though they are related: some escape sequences are introduced by an escape character. Others rely on a format.

<?php

    // \1 is an escape sequence that represents the first capturing parenthsis.
    // It is a special meaning for REGEX.
    preg_match('/(.)\1/', $string);

    // Displays AA
    echo "A\101";

?>

Documentation

See also String literals (MySQL), Lexical Structure (PostgreSQL) and INI file.

Related : Double Quotes Strings, Codepoint, E, Emoji, Escape Data