How can PHP be used to convert lowercase letters in a hash to uppercase letters?

To convert lowercase letters in a hash to uppercase letters in PHP, you can use the strtoupper() function to convert the entire string to uppercase. This will ensure that all lowercase letters in the hash are converted to uppercase.

$hash = "a1b2c3d4e5";

$uppercaseHash = strtoupper($hash);

echo $uppercaseHash;