Migrating from C/C++ to PHP - function to determine character type

In C/C++, the header file ctype.h defines a set of macros about character types, which can get the type of a given character.
There are no related functions in php. A few days ago, I discovered that the PHP downloaded from www.mm4.de provides an extension library called php_ctype.dll,
After loading, I found that some such functions are provided, which are specially compiled for your reference.
After loading the php_ctype.dll file correctly in PHP, use to see the following information:
ctype
ctype functions enabled (experimental)
Then you can use the functions it provides. The usage of all functions is basically the same as in C/C++. The difference is that the parameters of the function in C/C++ are
Character type (char), and in PHP, function parameters can be strings (string). For example:

$string="123ADAADAD";
if(isalnum($string))
{
echo "Only uppercase and lowercase letters and numbers!";
}

?>

Attached: Functions supported by php_ctype.dll
bool isalnum(string)
bool isalpha(string)
bool iscntrl(string)
bool isdigit(string)
bool isgraph(string)
bool islower(string)
bool isPRint(string)
bool ispunct(string)
bool isspace(string)
bool isupper(string)
bool isxdigit(string)

The above introduces the migration from C/C++ to PHP - the function to determine the character type, including the content of PHP determining the character type. I hope it will be helpful to friends who are interested in PHP tutorials.