What does the \x1a characters mean

Question

What does the \x1a character mean and why does mysql_real_escape_string escape it?

From the documentation:

mysql_real_escape_string() calls MySQL's library function mysql_real_escape_string, which prepends backslashes to the following characters: \x00, \n, \r, \, ', " and \x1a.

A ASCII Characters reference describes it as Substitute character, but this doesn't say much.

Answer 1

It's a Unicode escape sequence, in hexadecimal (base 16). \x1a is the "substitute" character.

See also: https://en.wikipedia.org/wiki/Substitute_character

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Why does mysql_real_escape_string escape it?

According to the documentation,

Strictly speaking, MySQL requires only that backslash and the quote character used to quote the string in the query be escaped. mysql_real_escape_string() quotes the other characters to make them easier to read in log files.

Answer 2

\x1A is CTRL+Z control character. It is also EOF marker.

Answer 3

\x1a is a SUB control character, used to mark end of a file (EOF).