Usted buscó: references' (Coreano - Chino (Simplificado))

see also references explained.
see also references explained.

is the character with octal code 113 (since there can be no more than 99 back references)
is the character with octal code 113 (since there can be no more than 99 back references)

the "schema" references the desired database schema (see sesam handbook).
the "schema" references the desired database schema (see sesam handbook).

/e modifier makes preg_replace() treat the replacement parameter as php code after the appropriate references substitution is done. tip: make sure that replacement constitutes a valid php code string, otherwise php will complain about a parse error at the line containing preg_replace().
preg_replace ("/( \/?)(\w+)([^ ]* )/e", "'\\1'.strtoupper('\\2').'\\3'", $html_body);