mb_substitute_character() specifies substitution character when input character encoding is invalid or character code is not exist in output character encoding. Invalid characters may be substituted NULL(no output), string or integer value (Unicode character code value).
This setting affects mb_convert_encoding(), mb_convert_variables(), mb_output_handler(), and mb_send_mail().
substchar
: Specify Unicode value as
integer or specify as string as follows
"none" : no output
"long" : Output character code value (Example: U+3000,JIS+7E7E)
Return Value: If substchar
is set, it
returns TRUE for success, otherwise returns
FALSE. If substchar
is
not set, it returns Unicode value or
"none"/"long".