How to create custom error messages in CakePHP validation?

@lizzie 

In CakePHP, you can create custom error messages for your validation rules using the message option in the validation rule definition.

To create a custom error message for a validation rule, follow these steps:

1. Define the validation rule in your model's validationDefault method.
2. Include the message option in the validation rule definition.
3. Use the special {} syntax to insert the field name and any other relevant variables into the error message.

Here's an example:

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// In your model's validationDefault method:
public function validationDefault(Validator $validator)
{
    $validator
        ->requirePresence('name')
        ->notEmptyString('name', 'Please enter a name')
        ->maxLength('name', 50, 'Name cannot be longer than 50 characters');

    return $validator;
}

In this example, we've defined three validation rules for the name field. The requirePresence and notEmptyString rules have default error messages, but the maxLength rule includes a custom error message.

The custom error message uses the {} syntax to insert the field name and the maximum length into the message. When this validation rule is triggered, the error message will look like this:

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Name cannot be longer than 50 characters

You can also use other variables in your custom error messages, such as the value of the field being validated. For example:

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$validator
    ->add('email', 'valid', [
        'rule' => 'email',
        'message' => 'Please enter a valid email address ({0})'
    ]);

In this example, the {0} syntax is used to insert the value of the email field into the error message, like this:

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Please enter a valid email address (invalid-email)

I hope this helps!