Symfony validation: How to validate user input in PHP applications

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$0 Summary
$1- Why ?
$2- Goal
$3- How ?
$4- What is a constraint ?
$5- Basic validation example
$6- Supported constraints
$7- The validator service
$8- Validation and Forms
$9- Translation constraint messages
$10- Constraint targets
$11- Validation groups
$12- Validating values
$13- How to create a custom validation constraint ?

$1 Why ?

Don't Trust
User Input

$1 Why ?
1. Validation is a very common task in web
applications.
2. Data entered in forms needs to be
validated.
3. Data also needs to be validated before it
is written into a database or passed to a
web service.

$2 Goal

The goal of validation is
to tell you whether or not
the data of an object is
valid.

$3 How ?
configure a list of rules (called constraints)
that the object must follow in order to be
valid.

These constraints can be specified via a
number of different formats (YAML, XML,
annotations, or PHP).

$4 Constraint

a constraint is simply a PHP object that
makes an assertive statement.

$5 Basic validation example
For example, to guarantee that the $name property is not
empty:

For example, to guarantee that the $name property is not
empty:

Imports constraints
namespace

Add NotBlank
constraint


The Symfony2 validator is enabled by default, but you must
explicitly enable annotations if you're using the annotation
method to specify your constraints:

$6 Supported constraints
Basic Constraints String Constraints Collection Constraints
 NotBlank  Email  Choice
 Blank  MinLength  Collection
 NotNull  MaxLength  UniqueEntity
 Null  Url  Language
 True  Regex  Locale
 False  Ip  Country
 Type

Number Constraints Date Constraints File Constraints Other Constraints
 Max  Date  File  Callback
 Min  DateTime  Image  All
 Time  Valid

$7 The validator service

To validate an object, use the
validate method on the validator service.

The job of the validator:

Is to read the constraints (i.e. rules) of a
class and verify whether or not the data
on the object satisfies those constraints.

If validation fails, an array of errors is
returned.


Each validation error (called a
constraint violation), is represented
by a ConstraintViolation object.

ConstraintViolation: http://api.symfony.com/2.0/Symfony/Component/Validator/ConstraintViolation.html

$8 Validation and Forms

Symfony's form library uses the
validator service internally to
validate the underlying object after
values have been submitted and
bound.

$8 Validation and Forms

The constraint violations on the
object are converted into FieldError
objects that can easily be displayed
with your form.

$9 Translating constraint messages

Create a translation file under the
validators catalog for the constraint
messages, typically in the
Resources/translations/ directory of
the bundle.

$9 Translating constraint messages

Constraint message

Constraint message

Translation message

$10 Constraint targets

Constraints can be applied to
a class property (e.g. name)
or a public getter method
(e.g. getFullName)

Properties:
The validator service allows you to validate private, protected or public
properties.
The example below shows you how to configure the $firstName property
of an Author class to have at least 3 characters:


Getters:
Constraints can also be applied to the return value of a
method.
Validator service allows you to add a constraint to any public
method whose name starts with “get” or “is”. In this guide,
both of these types of methods are referred to as “getters”.

Getters:


Some constraints apply to the entire class being
validated.
For example, the Callback constraint is a generic
constraint that's applied to the class itself. When that
class is validated, methods specified by that constraint
are simply executed so that each can provide more
custom validation.

$11 Validation groups
Question:
How to validate an object against
only some of the constraints on
that class ?

Answer:
Organize each constraint into one
or more “validation groups”, and
then apply validation against just
one or more group of constraints.

Example:
Suppose you have a User class,
which is used both when a user
registers and when a user updates
his/her contact information later:


With this configuration, there are two validation
groups:
 default: contains the constraints not
assigned to any other group;
 registration: contains the constraints on the
email and password fields only.


To tell the validator to use a specific group, pass
one or more group names as the second
argument to the validate() method:

validation groups in forms:
Controller:

Form Class:

$12 Validating values

you've seen how you can validate
entire objects. But sometimes, you
just want to validate a simple value -
like to verify that a string is a valid
email address.

$12 Validating values
verify that a string is a valid email address:
Import constraint Email

Create the consraint

Assigned the error message

Execute

Check for errors

How to create a custom validation
$13 constraint ?

http://symfony.com/doc/current/cookbook/
validation/custom_constraint.html

Symfony validation: How to validate user input in PHP applications

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