{"id":93,"date":"2021-03-08T00:17:32","date_gmt":"2021-03-08T00:17:32","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=93"},"modified":"2025-04-07T11:13:40","modified_gmt":"2025-04-07T11:13:40","slug":"php-constructors","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-oop\/php-constructors\/","title":{"rendered":"PHP Constructor"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you will learn how to use the PHP constructor to initialize the properties of an object.<\/p>\n\n\n\n

Introduction to the PHP Constructor #<\/a><\/h2>\n\n\n\n

PHP allows you to declare a constructor method for a class with the name __construct()<\/code> as follows:<\/p>\n\n\n

<?php<\/span>\n\nclass<\/span> ClassName<\/span>\n<\/span>{\n\tfunction<\/span> __construct<\/span>()<\/span>\n\t<\/span>{\n\t\t\/\/ implementation<\/span>\n\t}\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
When you create an instance of the class, PHP automatically calls the constructor method:<\/p>\n\n\n
$object = new<\/span> ClassName()<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Typically, you use the constructor to initialize the properties of the object.<\/p>\n\n\n\n
The following example defines a constructor for the BankAccount<\/code> class. The constructor initializes the $accountNumber<\/code> and $balance<\/code> properties:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n\tprivate<\/span> $accountNumber;\n\tprivate<\/span> $balance;\n\n\tpublic<\/span> function<\/span> __construct<\/span>($accountNumber, $balance)<\/span>\n\t<\/span>{\n\t\t$this<\/span>->accountNumber = $accountNumber;\n\t\t$this<\/span>->balance = balance;\n\t}\t\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Since the constructor has two parameters, you need to pass the corresponding arguments when creating a BankAccount<\/code> object:<\/p>\n\n\n
$account = new<\/span> BankAccount(1<\/span>, 100<\/span>);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, PHP automatically calls the __construct()<\/code> of the BankAccount<\/code> class. Hence, it assigns the $accountNumber<\/code> and $balance arguments<\/code> to the $accountNumber<\/code> and $balance<\/code> properties of the object.<\/p>\n\n\n\n
PHP constructor promotion #<\/a><\/h2>\n\n\n\n
In practice, you often need to assign the constructor arguments to corresponding properties. It’s kind of redundant. <\/p>\n\n\n\n
To improve this, PHP 8.0 introduced a new concept called constructor promotion that promotes the constructor’s arguments to properties.<\/p>\n\n\n\n
For example, instead of writing this:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n\tprivate<\/span> $accountNumber;\n\n\tprivate<\/span> $balance;\n\n\tfunction<\/span> __construct<\/span>($accountNumber, $balance)<\/span>\n\t<\/span>{\n\t\t$this<\/span>->accountNumber = $accountNumber;\n\t\t$this<\/span>->balance = $balance;\n\t}\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
you can use this:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n\tfunction<\/span> __construct<\/span>( private $accountNumber, private $balance)<\/span>\n\t<\/span>{\t\n\t}\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Sometimes, if you don’t want to promote constructor arguments, you can remove the access modifier. For example:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n\tfunction<\/span> __construct<\/span>(private $accountNumber, private $balance, $type)<\/span>\n\t<\/span>{\t\n \t}\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, the $type<\/code> argument doesn’t include the access modifier. Therefore, it’s a regular parameter and won’t be promoted to a property.<\/p>\n\n\n\n
Notice that the order of promoted-argument and non-promoted arguments can appear in the constructor in any order.<\/p>\n\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
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  • PHP constructor is a special method that is called automatically when an object is created.<\/li>\n\n\n\n
  • Do use constructor promotion as much as possible to make the code shorter.<\/li>\n<\/ul>\n
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When a constructor parameter includes an access modifier<\/a> (public<\/code>, private<\/code>, or protected<\/code>) PHP will treat it as both a constructor’s argument and an object’s property. And it assigns the constructor argument to the property. <\/p>\n\n\n\n