➤ The ctype_upper() function used to check each and every character of a given string is in upper case or not. If the string in upper case then it returns TRUE otherwise returns False. Syntax:

ctype_upper (string text)

For intsnace:

$string = "IAMHUNGRYYYYYY";
$result = ctype_upper ($string);
echo $result;
// outputs :   1  (True)
// All characters of  "IAMHUNGRYYYYYY" in UPPERCASE

➤ The ctype_lower() function used to check each and every character of a given string is in lower case or not.