The idea and specific implementation of PHP regular judgment of Chinese UTF-8 or GBK_PHP tutorial

UTF-8 matching: In JavaScript, it is very simple to determine whether a string is Chinese. For example:

Copy code The code is as follows:

var str = "php programming";
if (/^[ u4e00-u9fa5]+$/.test(str)) {
alert("This string is all in Chinese");
}else{
alert("This string is not all in Chinese") ;
}
//In php, x is used to represent hexadecimal data. So, transform it into the following code:
$str = "php programming";
if (preg_match("/^[x4e00-x9fa5]+$/",$str)) {
print(" The string is all in Chinese");
} else {
print("The string is not all in Chinese");
}

It seems that no error is reported, judge The result is also correct, but if $str is replaced with the word "programming", the result still shows "not all of the string is Chinese". It seems that this judgment is not accurate enough. Important: After consulting "Proficient in Regular Expressions", I found that for [x4e00-x9fa5], I made an enhanced explanation myself. In PHP's regular expressions, [x4e00-x9fa5] is actually the concept of characters and character groups. x{hex}, expresses a hexadecimal number. It should be noted that hex can be 1-2 digits or 4 digits, but if it is 4 digits, curly brackets must be added. At the same time, if it is greater than x The hex of {FF} must be used together with the u modifier, otherwise an illegal error will occur
On the Internet, you can only find regular rules for matching full-width characters: ^[x80-xff]*^/, you don’t need to add braces here
[ u4e00-u9fa5] can match Chinese, but PHP does not support
However, since the hexadecimal data represented by x, why is it different from the range x4e00-x9fa5 provided in js? So I changed to the code below and found that it was really accurate:

Copy the code The code is as follows:

$str = "php programming";
if (preg_match("/^[x{4e00}-x{9fa5}]+$/u",$str)) {
print("The string is all in Chinese ");
} else {
print("This string is not all in Chinese");
}

I know the regular expression for utf-8 encoding in php The final correct expression for matching Chinese characters - /^[x{4e00}-x{9fa5}]+$/u,

wrote the following test code with reference to the above article (copy the following code and save it as. php file)

Copy code The code is as follows:

$action = trim($_GET[ 'action']);
if($action == "sub")
{
$str = $_POST['dir'];
//if(!preg_match("/^ [".chr(0xa1)."-".chr(0xff)."A-Za-z0-9_]+$/",$str)) //GB2312 Chinese character alphanumeric underline regular expression
if( !preg_match("/^[x{4e00}-x{9fa5}A-Za-z0-9_]+$/u",$str)) //UTF-8 Chinese character alphanumeric underline regular expression
{
echo "The [".$str."] you entered contains illegal characters";
}
else
{
echo " The [".$str."] you entered is completely legal and passed!";
}
}
?>

Copy code The code is as follows:

Input characters (numbers, letters, Chinese characters, underscores):

GBK: preg_match("/^[".chr(0xa1)."-".chr(0xff)."A- Za-z0-9_]+$/",$str); //GB2312 Chinese character alphanumeric underline regular expression.

http://www.bkjia.com/PHPjc/621720.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/621720.htmlTechArticleUTF-8 matching: In javascript, it is very simple to determine whether a string is Chinese. For example: Copy the code as follows: var str = "php programming"; if (/^[u4e00-u9fa5]+$/.test(str)) { alert(...