Implementation code to determine whether a string is all Chinese or contains Chinese in PHP

First, the judgment is all in Chinese
The code is as follows:
$str="'324 is";
if(!eregi("[^x80-xff]","$str")){
echo "All in Chinese" ;
}else{
echo "is not";
}

Second, determine whether it contains Chinese
The code is as follows:
$str = "Chinese";
if (preg_match("/[x7f-xff]/", $str) ) {
echo "Contains Chinese";
}else{
echo "No Chinese";
}
or
$pattern = '/[^x00-x80]/';
if(preg_match($pattern,$str) ){
echo "Contains Chinese";
}else{
echo "No Chinese";
}

I tested these methods under utf-8 and have not tested them under other encodings.