Php judges Chinese and English characters

Encoding table

Double byte character encoding range

1. gbk (gb2312/gb18030)
X00-xff gbk dubyte encoding range
X20-x7f (ascii)
Xa1-xff Chinese gb2312
X80-xff Chinese gbk

2. UTF-8 (unicode)

U4e00-u9fa5)
X3130-x318f (Korean
Xac00-xd7a3 (Korean)
U0800-u4e00 (Japanese)

<?
$ Str = "China ";
Echo $ str;
Echo "// If (preg_match ("/^ [". chr (0xa1 ). "-". chr (0xff ). "] + $/", $ str) {// can only be used in the case of gb2312
If (preg_match ("/^ [x7f-xff] + $/", $ str) {// compatible with gb2312, UTF-8
Echo "correct input ";
} Else {
Echo "incorrect input ";
}
?>

There are actually a lot of knowledge about Chinese judgment problems. The underlying internal encoding involves UTF-8, gbk, and gb13800. I have studied how to differentiate what a character is. There are too many associated details.