`$validates_presence_of` Validation¶

The $validates_presence_of validation in ActiveRecord allows you to validate whether an attribute's value is present or not. It ensures that the attribute is not empty or null unless specific conditions are met. To use $validates_presence_of, you need to specify the following options:

Attribute Name: This option specifies the name of the attribute you want to validate for presence. It is typically set as a symbol or string.
```
static $validates_presence_of = ['name' => []];
```
Allow Null (Optional): The allow_null option allows you to specify whether the attribute is allowed to be null. By default, allow_null is set to false, meaning that the attribute must not be null. You can set it to true to allow null values.
```
static $validates_presence_of = [
    'middle_name' => [
        'allow_null' => true
    ]
];
```
Allow Blank (Optional): The allow_blank option allows you to specify whether the attribute is allowed to be empty (e.g., an empty string). By default, allow_blank is set to false, meaning that the attribute must not be blank. You can set it to true to allow blank values.
```
static $validates_presence_of = [
    'comments' => [
        'allow_blank' => true
    ]
];
```
Message (Optional): To customize the error message displayed when the validation fails, you can use the message option to provide a custom error message.
```
static $validates_presence_of = [
    'email' => [
        'message' => 'Email address is required'
    ]
];
```
On (Optional): The on option allows you to specify when the validation should occur. By default, it is set to 'save', which means the validation is performed when the record is saved. You can set it to 'create' to validate only during the creation of a new record or 'update' to validate only during updates.
```
static $validates_presence_of = [
    'address' => [
        'on' => 'create'
    ]
];
```

Example of Usage:

```php class User extends ActiveRecord\Model { static $validates_presence_of = [ 'username' => ['allow_blank' => true], 'email' => ['allow_null' => true], 'first_name' => [], ]; }

$validates_presence_of Validation¶

`$validates_presence_of` Validation¶