base\Model rules()

Returns the validation rules for attributes.

Validation rules are used by validate() to check if attribute values are valid. Child classes may override this method to declare different validation rules.

Each rule is an array with the following structure:

[
    ['attribute1', 'attribute2'],
    'validator type',
    'on' => ['scenario1', 'scenario2'],
    //...other parameters...
]

where

• attribute list: required, specifies the attributes array to be validated, for single attribute you can pass a string;
• validator type: required, specifies the validator to be used. It can be a built-in validator name, a method name of the model class, an anonymous function, or a validator class name.
• on: optional, specifies the scenarios array in which the validation rule can be applied. If this option is not set, the rule will apply to all scenarios.
• additional name-value pairs can be specified to initialize the corresponding validator properties. Please refer to individual validator class API for possible properties.

A validator can be either an object of a class extending yii\validators\Validator, or a model class method (called inline validator) that has the following signature:

// $params refers to validation parameters given in the rule
function validatorName($attribute, $params)

In the above $attribute refers to the attribute currently being validated while $params contains an array of validator configuration options such as max in case of string validator. The value of the attribute currently being validated can be accessed as $this->$attribute. Note the $ before attribute; this is taking the value of the variable $attribute and using it as the name of the property to access.

Yii also provides a set of built-in validators. Each one has an alias name which can be used when specifying a validation rule.

Below are some examples:

[
    // built-in "required" validator
    [['username', 'password'], 'required'],
    // built-in "string" validator customized with "min" and "max" properties
    ['username', 'string', 'min' => 3, 'max' => 12],
    // built-in "compare" validator that is used in "register" scenario only
    ['password', 'compare', 'compareAttribute' => 'password2', 'on' => 'register'],
    // an inline validator defined via the "authenticate()" method in the model class
    ['password', 'authenticate', 'on' => 'login'],
    // a validator of class "DateRangeValidator"
    ['dateRange', 'DateRangeValidator'],
];

Note, in order to inherit rules defined in the parent class, a child class needs to merge the parent rules with child rules using functions such as array_merge().

See also scenarios().