PHP removes illegal UTF-8 characters

//reject overly long 2 byte sequences, as well as characters above u+10000 and replace with?$some _string = Preg_replace ('/[x00-x08x10x0bx0cx0e-x19x7f]'. '| [x00-x7f] [X80-xbf]+'. '| ([xc0xc1]| [Xf0-xff]) [X80-xbf]*'. '| [XC2-XDF] ((?! [X80-XBF]) | [X80-XBF] {2,})'. '| [Xe0-xef] ([X80-XBF] (?! [X80-XBF]) | (?! [X80-XBF] {2}) | [X80-XBF] {3,}) /S', '?', $some _string);//reject overly long 3 byte sequences and UTF-16 surrogates and replace with?$some _string = Preg_replace ('/XE0[X80-X9F][X80-XBF]'. '|xed[xa0-xbf][x80-xbf]/s','?', $some _string);

PHP removes illegal UTF-8 characters