36 lines
1,012 B
Markdown
36 lines
1,012 B
Markdown
---
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title: >
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Immutable read-only properties in PHP 8.1
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pubDate: 2023-04-13
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permalink: >-
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daily/2023/04/13/immutable-read-only-properties-in-php-8-1
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tags:
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- php
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---
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Continuing with yesterday's data transfer object (DTO) example, something that can be done since PHP 8.1 is to make properties read-only:
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```language-php
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class AccountDetails {
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public function __construct(
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public readonly string $accountNumber,
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public readonly string $sortCode,
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) {}
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}
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```
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This means the public properties can be read and used without the need for getter methods, but cannot be overridden - making the DTO immutable.
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Without `readonly`, a DTO can be created and the property values can be changed:
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```language-php
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$accountDetails = new AccountDetails('12345678', '00-00-00');
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$accountDetails->accountNumber = 'banana';
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```
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With `readonly` set, you'd get a fatal error instead:
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> Fatal error: Uncaught Error: Cannot modify readonly property AccountDetails::$accountNumber in /home/opdavies/tmp/example.php:13
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