string_utf8_offset [function]

string_utf8_offset( string ustr, int charnum[, int byteoff ])

returns byte offset of character in UTF-8 string, optionally skipping the specified number of bytes

• valid character numbers are 0 to actual number of characters from specified byte offset
• valid byte offsets are 0 to ustr.length

string_utf8_offset( "標準", 2 ); // returns 6