PHP Regular Expression judgment Chinese UTF-8 & GBK

UTF-8 matching: In JavaScript, it is very easy to judge that the string is Chinese. For example:
VaR STR = "PHP programming ";
If (/^ [\ u4e00-\ u9fa5] + $/. Test (STR )){
Alert ("all strings are Chinese ");
}
Else {
Alert ("Not all strings are Chinese ");
} In PHP, \ x is used to represent hexadecimal data. Therefore, it is transformed into the following Code :
$ STR = "PHP programming ";
If (preg_match ("/^ [\ x4e00-\ x9fa5] + $/", $ Str )){
Print ("all strings are Chinese ");
} Else {
Print ("Not all strings are Chinese ");
}
It seems that no error is reported, and the result is correct. However, if you replace $ STR with "programming", the result still shows "Not all the strings are Chinese ", it seems that such judgment is not accurate enough. Important: I checked the <proficient Regular Expression> and found that for [\ x4e00-\ x9fa5], I made an enhanced explanation of PHP's regular expression, [\ x4e00-\ x9fa5] is actually the concept of character and character group. \ x {hex} represents a hexadecimal number, note that hex can be 1-2 bits or 4 bits, but if it is 4 bits, it must be enclosed by braces. If it is a hex larger than X {ff, must be used with the U modifier. Otherwise, an error will occur.
Only regular expressions matching the full-width characters can be found on the Internet: ^ [\ X80-\ xFF] * ^/. brackets are not added here.
[\ U4e00-\ u9fa5] can match Chinese characters, but PHP does not support
However, since \ x represents the hexadecimal data, why is the range \ x4e00-\ x9fa5 different from that provided in JS? So I switched to the following code and found that it was really accurate:
$ STR = "PHP programming ";
If (preg_match ("/^ [\ x {4e00}-\ x {9fa5}] + $/u", $ Str )){
Print ("all strings are Chinese ");
} Else {
Print ("Not all strings are Chinese ");
} The final correct expression for matching Chinese characters using regular expressions in PHP in UTF-8 encoding --/^ [\ x {4e00}-\ x {9fa5}] + $/u,
Refer to the aboveArticle I wrote the following test code (copy the following code and save it as a. php file) <? PHP
$ Action = trim ($ _ Get ['action']);
If ($ action = "sub ")
{
$ STR = $ _ post ['dir'];
// If (! Preg_match ("/^ [". CHR (0xa1 ). "-". CHR (0xff ). "A-Za-z0-9 _] + $/", $ Str) // gb2312 Regular Expression of Chinese characters, letters, numbers, underscores (_)
If (! Preg_match ("/^ [\ x {4e00}-\ x {9fa5} A-Za-z0-9 _] + $/u", $ Str) // UTF-8 Chinese characters, letters, numbers, underscores, regular expressions
{
Echo "<font color = Red> The [". $ Str. "] You entered contains illegal characters </font> ";
}
Else
{
Echo "<font color = green> The [". $ Str. "] You entered is completely legal. Pass! </Font> ";
}
}
?>
<Form. method = "Post" Action = "? Action = sub ">
Input characters (numbers, letters, Chinese characters, and underlines ):
<Input type = "text" name = "dir" value = "">
<Input type = "Submit" value = "Submit">
</Form> GBK: preg_match ("/^ [". CHR (0xa1 ). "-". CHR (0xff ). "A-Za-z0-9 _] + $/", $ Str); // Regular Expression of gb2312 Chinese characters, letters, numbers, underscores.