PHP Tutorial - PHP Form Validation

Basic input validation in PHP is done using the following functions.

  • is_string(),
  • is_numeric(),
  • is_float(),
  • is_array(), and
  • is_object().

Each of these functions take a variable and return true if that variable is of the appropriate type.

The three basic validation checks we should do.

  • whether we have required variables,
  • whether the variables have a value assigned, and
  • whether they have the the type we are expecting.

After the basic check, we can do more check, such as integer value range, the string length, count of array elements, etc.

CTYPE functions

There are eleven CTYPE functions in total. they work in the same way as is_numeric().

Function Meaning
ctype_alnum() Matches A?Z, a?z, 0?9
ctype_alpha() Matches A?Z, a?z
ctype_cntrl() Matches ASCII control characters
ctype_digit() Matches 0?9
ctype_graph() Matches values that can be represented graphically
ctype_lower() Matches a?z
ctype_print() Matches visible characters (not whitespace)
ctype_punct() Matches all non-alphanumeric characters (not whitespace)
ctype_space() Matches whitespace (space, tab, new line, etc.)
ctype_upper() Matches A?Z
ctype_xdigit() Matches digits in hexadecimal format

$var = "123456789a";
print (int)ctype_digit($var);


The following code checks whether the $Age variable has a numeric value between 18 and 30.

if (isset($Age)) {
        if (is_numeric($Age)) {
                if (($Age > 18) && ($Age < 30)) {
                        print " input is valid";
                } else {
                        print "Sorry, you're not the right age!";
        } else {
                print "Age is incorrect!"
} else {
        print "Please provide a value for Age.";