How can we check if the value of a given variable is alphanumeric?

To check if the value of a given variable is alphanumeric in PHP, you can use the ctype_alnum() function. The ctype_alnum() function returns true if all characters in the string are alphanumeric (letters or digits), and false otherwise. It can be used to validate user input or check if a variable contains only alphanumeric characters. For example, you can use ctype_alnum($var) to check if the value of $var is alphanumeric. It's important to note that the ctype_alnum() function only works with string values. If you need to check alphanumericity for numeric values, you can use a combination of is_string() and is_numeric() functions.