Form: Serverside validation rules

docs/general-concepts/forms/server-side-validation.md

@@ -25,7 +25,82 @@ This is triggered by specifying a `validate=...` attribute in your form definiti
 ```
 The `validate="tel"` line triggers the validation on this field, and it will use the `test` function in TelRule in libraries/src/Form/Rule to check if the field value is valid. 
 
-You can see the list of validation rules that Joomla provides by looking at the class files in the libraries/src/Form/Rule directory, and choose what validation routine you want to run against the fields in your form. For example, to use the EmailRule you would include `validate="email"` against the email field in your form definition. 
+### List of available validation rules
+You can see the list of validation rules that Joomla provides by looking at the class files in the `libraries/src/Form/Rule` directory. Following is a list of all those rules. The title of the entry is the string you have to use in the `validate` attribute.
+
+#### boolean
+Checks the value to be either `1`, `0`, `true` or `false`.
+
+#### calendar
+Checks the value to be either `now` or a value which the PHP DateTime object accepts.
+
+#### captcha
+Validates the value against a captcha solution. This rule has the optional attributes `plugin` and `namespace` to force a specific captcha plugin. If not set, the globally set captcha will be used.
+
+#### color
+Checks if the string is 3 or 6 characters long and consists of hexadecimal characters.
+
+#### cssidentifier/cssidentifiersubstring
+Checks if the string is a (series of) valid CSS identifiers.
+
+#### email
+Check if the string is a valid e-mail adress.
+If the attribute `tld` is set to `tld` or `required`, a TLD with at least 2 characters is required. 
+If the attribute `validDomains` is set to a component name and field name, it tries to load a list of valid domains from the component configuration of said component. The default value is `com_users.domains`. The field supports validating multiple e-mail adresses when the attribute `multiple` is set.
+By setting the attribute `unique`, it checks if the adress is already in use in the `#__users` table.
+
+#### equals/notequals
+Compares the value to another field of the form given by the `field` attribute.
+
+#### exists
+Checks if the value is present in a database table. The table to check is controlled by `exists_table` and the column by `exists_column`. If the column is not given, it defaults to `id`.
+
+#### filepath
+Checks if the value is a valid file path. This does NOT check if the file exists, just that the path is inside of the Joomla folder. You can define a list of folders (separated by the pipe symbol (`|`)) to exclude by setting the `exclude` attribute.
+
+#### folderpathexists
+Checks if the given path is a valid folder from the root of the Joomla installation and if that folder exists.
+
+#### modulelayout
+This checks if the string is valid as a module layout name
+
+#### number
+Checks if a number is in a certain range between a `min` and `max` value. These attributes are optional and the comparison is done with float values.
+
+#### options
+Checks if the value is from the given options of the field.
+
+#### password
+Ensures the given string meets the password requirements set in Joomla.
+
+#### regex
+Allows to validate against a regular expression, which is given by `validate_regex`.
+
+#### rules
+Ensures that all actions posted are valid for this field.
+
+#### showon
+Ensures the given string is in valid `showon` format.
+
+#### subform
+Allows to validate subforms field by field.
+
+#### tel
+Validate an input as a telephone number. You can influence this by using the attribute `plan`, which allows for the values `northamerica`, `us`, `International`, `int`, `missdn` or `IETF`.
+
+#### time
+Validate the input as a valid time. You can limit the valid values by setting the attributes `min`, `max` and `step`.
+
+#### url
+Validates the input as a URL and checks for XSS attacks. You can disabled the XSS checks by setting the attribute `disableXssCheck`. You can limit valid values further by setting the attributes `schemes` and `relative`.
+
+#### userid
+Checks if the input is a valid user ID.
+
+#### username
+Checks if the username is unique in the `#__users` table.
+
+
 ### Custom Server-side Validation
 You can define your own validation for a field by writing a custom validation rule. We'll take as an example a custom rule called "custom" which we'll use to replace the Joomla-provided telephone number validation. You can obviously call your own rule whatever you like. Then you have to do 3 things:
 - In your field definition against the field add the attribute `validate="custom"` against your field
@@ -120,4 +195,4 @@ class TelephoneRule extends FormRule
         return false;
     }
 }
-```
+```