PHP's Ctype Functions

ctypes-alpha-alnum.php

<?php
// Check if input is alphanumeric (letters and numbers)
ctype_alnum('abcdef1234'); // This returns TRUE
ctype_alnum('£%^&ab2'); // This on the otherhand returns FALSE

// check if input is alpha (letters)
ctype_alpha('dssfsdf'); // returns TRUE
ctype_alpha('12345dssfsdf'); // Returns FALSE
?>

digit-upper-lower.php

<?php
// Check if the input is numeric
ctype_digit('1234'); // TRUE
ctype_digit('1as2d34f'); // FALSE

// Uppercase
ctype_upper('HELLO'); // TRUE
ctype_upper('hElLo'); // FALSE

// Lowercase
ctype_lower('hello'); // TRUE
ctype_lower('HeLLo'); // FALSE
?>