A Guide to the PHP property_exists() function by Practical Examples (original) (raw)

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 <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>o</mi><mi>b</mi><mi>j</mi><mi>e</mi><mi>c</mi><msub><mi>t</mi><mi>o</mi></msub><msub><mi>r</mi><mi>c</mi></msub><mi>l</mi><mi>a</mi><mi>s</mi><mi>s</mi><mo separator="true">,</mo><mi>s</mi><mi>t</mi><mi>r</mi><mi>i</mi><mi>n</mi><mi>g</mi></mrow><annotation encoding="application/x-tex">object_or_class, string </annotation></semantics></math>objectorclass,stringproperty): 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.

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')); // false`Code 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=>key => key=>value) { if (property_exists($this, $key)) { this−>this->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]](/cdn-cgi/l/email-protection)', '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.

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