PHP Chinese string interception function

/****First of all, it is the boss of CSDN Forum PHP xuzuning (nagging), which supports three encodings: gb2312, gbk, and big.
Here is the code: ***/
$len = 19;
$text = "How to display only the first few words of a long news title and replace it with...?";
 echo strlen($text)<=$len ? $text : (substr($text,0,$len).chr(0)."....");
/****chr(0) is not null
null means nothing, and the value of chr(0) is 0. Expressed in hexadecimal it is 0x00, expressed in binary it is 00000000
Although chr(0) will not display anything, it is a character.
When a Chinese character is truncated, according to the encoding rules, it always has to pull in other characters behind it and interpret them as Chinese characters. This is the reason why garbled characters appear. The combination of values ​​0x81 to 0xff and 0x00 is always displayed as "empty"
According to this feature, adding a chr (0) after the result of substr can prevent garbled characters
Note:
Encode the first byte Second byte
gb2312 0xa1-0xf7 0xa1-0xfe
gbk 0x81-0xfe 0x81-0xfe 0x40-0x7e
big5 0xa1-0xf7 0x81-0xfe 0x40-0x7e
Secondly, this was searched online and supports utf-8 encoding. The original author Unknown:
 *****/
 function subString_UTF8($str, $start, $lenth)
 {
 $len = strlen($str);
 $r = array();
 $n = 0;
 $m = 0;
 for($i = 0; $i < $len; $i++) {
 $x = substr($str, $i, 1);
 $a = base_convert(ord($x), 10, 2);
 $a = substr ('00000000'.$a, -8);
 if ($n < $start){
 if (substr($a, 0, 1) == 0) {
 }elseif (substr($a, 0 , 3) == 110) {
 $i += 1;
 }elseif (substr($a, 0, 4) == 1110) {
 $i += 2;
 }
 $n++;
 }else{
 if (substr($a, 0, 1) == 0) {
 $r[ ] = substr($str, $i, 1);
 }elseif (substr($a, 0, 3) == 110 ) {
 $r[ ] = substr($str, $i, 2);
 $i += 1;
 }elseif (substr($a, 0, 4) == 1110) {
 $r[ ] = substr($str, $i, 3);
 $i += 2;
 }else{
 $r[ ] = '';
 }
 if (++$m >= $lenth){
 break;
 }
 }
 }
 return $r;
 } // End subString_UTF8;
}// End String

#Since this function returns an array, the join function must be used to display the string:
#join( '',subString_UTF8($str, $start, $lenth));
#You can also append a "..." after this statement when the page is displayed