Available Validation Rules
The PHP validation script comes with functions for all commonly needed validation tasks - things like ensuring email addresses are valid, fields are required and so forth. You can run multiple tests on a single field if you need. To give you an idea of what validation rules available, give the following table a quick look over. In the next step we'll start working on adding some of these rules to validate a simple form.
required
field must be filled in
digits_only
field must contain digits only
length=X
field has to be X characters long
length=X-Y
field has to be between X and Y (inclusive) characters long
length>X
field has to be greater than X characters long
length>=X
field has to be greater than or equal to X characters long
length<X
field has to be less than X characters long
length<=X
field has to be less than or equal to X characters long
valid_email
field has to be valid email address
same_as
fieldname is the same as fieldname2 (for password comparison)
range=X-Y
field must be a number between the range of X and Y inclusive
range>X
field has to be a number greater than X
range>=X
field has to be a number greater than or equal to X
range<X
field has to be a number less than X
range<=X
field has to be a number less than or equal to X
is_alpha
field has to be an alphanumeric character (anything between 0-9, a-Z)
letters_only
field has to be a letter, a-Z
custom_alpha
This option is a layman's version of the reg_exp rule and offers more control
than the letters_only rule. It lets you check that a field is formatted in a
very specific way - like a specific series of integers and digits.
reg_exp
field is validated according to a regular expression (programmers only)