{"id":2604,"date":"2021-09-06T09:20:20","date_gmt":"2021-09-06T09:20:20","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=2604"},"modified":"2025-04-07T11:17:22","modified_gmt":"2025-04-07T11:17:22","slug":"php-typed-properties","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-oop\/php-typed-properties\/","title":{"rendered":"PHP Typed Properties"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you wil learn how to define typed properties by adding type hints to class properties.<\/p>\n\n\n\n

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

The following example defines the BankAccount<\/code> class<\/a> with a property called $balance<\/code>:<\/p>\n\n\n

class<\/span> BankAccount<\/span>\n<\/span>{\n    public<\/span> $balance;\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
The default value of the $balance<\/code> property is null<\/code>.<\/p>\n\n\n
$account = new<\/span> BankAccount();\nvar_dump($account->balance); \/\/ null<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
PHP 7.4 allows you to type hints<\/a> the class properties with any types except void<\/code> and callable<\/code>. For example:<\/p>\n\n\n
class<\/span> BankAccount<\/span>\n<\/span>{\n    public<\/span> float $balance;\n}<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
$account = new<\/span> BankAccount();\nvar_dump($account->balance);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Error:<\/p>\n\n\n
Fatal error: Uncaught Error: Typed property BankAccount::$balance must not be accessed before initialization<\/code><\/span>Code language:<\/span> plaintext<\/span> (<\/span>plaintext<\/span>)<\/span><\/small><\/pre>\n\n\n
It doesn’t work because the $balance<\/code> property now becomes uninitialized<\/em>. The default value of the $balance<\/code> property is not null<\/code> like before. <\/p>\n\n\n\n
Notice that you can still create a new object with typed properties uninitialized.<\/p>\n\n\n\n
To read from a typed property, you need to initialize it first. For example:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n    public<\/span> float $balance;\n}\n\n$account = new<\/span> BankAccount();\n$account->balance = 0<\/span>;\n\nprint<\/span>($account->balance); \/\/ 0<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
For properties with scalar types, you can initialize them in the declaration. For example:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n    public<\/span> float $balance = 0<\/span>;\n}\n\n$account = new<\/span> BankAccount();\nprint<\/span>($account->balance); \/\/ 0<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Alternatively, you can initialize the typed properties in the constructor<\/a> of the class:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n    public<\/span> float $balance = 0<\/span>;\n\n    public<\/span> function<\/span> __construct<\/span>(float $balance)<\/span>\n    <\/span>{\n        $this<\/span>->balance = $balance;\n    }\n}\n\n$account = new<\/span> BankAccount(100<\/span>);\nprint<\/span>($account->balance); \/\/ 100<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
If you unset a typed property, its status will change back to uninitialized. Note that for an untyped property, its value will become null<\/code> after unset. For example:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n    public<\/span> float $balance = 0<\/span>;\n\n    public<\/span> function<\/span> __construct<\/span>(float $balance)<\/span>\n    <\/span>{\n        $this<\/span>->balance = $balance;\n    }\n}\n\n$account = new<\/span> BankAccount(0<\/span>);\necho<\/span> $account->balance; \/\/ 0<\/span>\n\nunset<\/span>($account->balance);\necho<\/span> $account->balance; \/\/ error<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Typed properties and strict types #<\/a><\/h2>\n\n\n\n
In the following example, the constructor<\/a> of the BankAccount<\/code> expects a float<\/code>. However, you can pass a string<\/a>. In this case, PHP coerces the string to a float:<\/p>\n\n\n
<?php<\/span>\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n    public<\/span> float $balance = 0<\/span>;\n\n    public<\/span> function<\/span> __construct<\/span>(float $balance)<\/span>\n    <\/span>{\n        $this<\/span>->balance = $balance;\n    }\n}\n\n$account = new<\/span> BankAccount(\"100.5\"<\/span>);\necho<\/span> $account->balance; \/\/ 100.5<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
If you don’t want this behavior, you can disable it by declaring strict_types<\/a><\/code> at the beginning of the file as follows:<\/p>\n\n\n
<?php<\/span>\n\ndeclare<\/span>(strict_types=1<\/span>);\n\nclass<\/span> BankAccount<\/span>\n<\/span>{\n    public<\/span> float $balance = 0<\/span>;\n\n    public<\/span> function<\/span> __construct<\/span>(float $balance)<\/span>\n    <\/span>{\n        $this<\/span>->balance = $balance;\n    }\n}\n\n$account = new<\/span> BankAccount(\"100.25\"<\/span>); \/\/ error<\/span>\nvar_dump($account->balance);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Error:<\/p>\n\n\n
Fatal error: Uncaught TypeError: Argument 1 passed to BankAccount::__construct() must be of the type float, string given.<\/code><\/span>Code language:<\/span> plaintext<\/span> (<\/span>plaintext<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
    \n
  • Typed properties include modifiers (private<\/code>, protected<\/code>, and public<\/code>) and types (except void<\/code> and callable<\/code>).<\/li>\n\n\n\n
  • Typed properties have uninitialized states, not null like untyped properties.<\/li>\n<\/ul>\n
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    Did you find this tutorial useful?<\/div>\n\t\t
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Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
Try it<\/a><\/p>\n\n\n\n
In this example, the $balance<\/code> property has the type float<\/a><\/code>. When you add the float<\/code> type to $balance<\/code> property, the following code causes an error:<\/p>\n\n\n
Try it<\/a><\/p>\n\n\n\n