I simulated it:
<?php
$text = 'Äpfel';
mb_internal_encoding( 'utf-8' );
printf( "%d\n", mb_eregi( 'äpfel', $text ) ); // Output: 0
printf( "%d\n", mb_ereg( 'äpfel', mb_strtolower( $text ) ) ); // Output: 1
printf( "%d\n", mb_eregi( 'äpfel', mb_strtolower( $text ) ) ); // Output: 1
?>
mb_eregi
(PHP 4 >= 4.2.0, PHP 5)
mb_eregi — Regular expression match ignoring case with multibyte support
Descrição
Executes the case insensitive regular expression match with multibyte support.
Parâmetros
Valor Retornado
Executes the regular expression match with multibyte support, and returns 1 if matches are found. If the optional regs parameter was specified, the function returns the byte length of matched part, and the array regs will contain the substring of matched string. The function returns 1 if it matches with the empty string. If no matches are found or an error happens, FALSE will be returned.
Notas
Nota:
A codificação interna ou a codificação de caractere especificado por mb_regex_encoding() será usado como a codificação de caractere para esta função.
Veja Também
- mb_regex_encoding() - Returns current encoding for multibyte regex as string
- mb_ereg() - Regular expression match with multibyte support
mb_eregi
20-Feb-2012 08:31
27-Aug-2010 04:44
This function does not work - it is not case insensitive for non latin characters.
10-Apr-2003 04:52
When this function is perfected, and is not experimental, it may be very usefull in the searching and pinpointing of places inside large text files.

mb_eregi_replace