PHP property_exists

Summary: in this tutorial, you’ll learn how to use the property_exists() function to check if the object or class has a property.

Introduction to the PHP property_exists function

The property_exists() function returns true if an object or a class has a property. Otherwise, it returns false.

Here’s the syntax of the property_exists() method:

property_exists(object|string $object_or_class, string $property): boolCode language: PHP (php)

The property_exists() method has two parameters:

• The $object_or_class specifies the object or class that needs to check for the existence of a property.
• The $property specifies the name of the property to check.

Note that in case of an error, the property_exists() function returns null instead.

PHP property_exists function examples

The following example uses the property_exists() function to check if the FileReader class has a specific property:

<?php

class FileReader
{
    private $filename;

    public $done;

    protected $filesize;

    public static $mimeTypes;
}

var_dump(property_exists(FileReader::class, 'filename')); // true
var_dump(property_exists(FileReader::class, 'done')); // true
var_dump(property_exists(FileReader::class, 'filesize')); // true
var_dump(property_exists(FileReader::class, 'mimeTypes')); // true

var_dump(property_exists(FileReader::class, 'status')); // falseCode language: PHP (php)

PHP property_exists function practical example

Suppose that you have a base class called Model. All the model classes need to extend this Model class.

To load a Model object from an associative array, you can define a load() method in the Model class as follows:

<?php

abstract class Model
{
    public function load(array $data): self
    {
        foreach ($data as $key => $value) {
            if (property_exists($this, $key)) {
                $this->$key = $value;
            }
        }

        return $this;
    }
}Code language: PHP (php)

The load() method accepts an associative array as an argument. It iterates over the array element. If the object has a property that matches a key in the array, the load() method assigns the value to the property.

The following defines the User class that extends the Model class:

class User extends Model
{
    private $username;

    private $email;

    private $password;
}Code language: PHP (php)

To populate the properties of the User class with values of an array, you call the load() method like this:

$user = (new User())->load([
    'username' => 'john',
    'email' => '[email protected]',
    'password' => password_hash('VerySecurePa$$1.', PASSWORD_DEFAULT),
]);Code language: PHP (php)

In practice, you would have a registration form. After the form is submitted, you need to validate the data in the $_POST array. And then you call the load() method to initialize a User object.

Summary

• Use the PHP property_exists() function to check if an object or a class has a specific property.