PHP Internals News: Episode 90: Read Only Properties
In this episode of "PHP Internals News" I chat with Nikita Popov (Twitter, GitHub, Website) about the "Read Only Properties" RFC.
The RSS feed for this podcast is https://derickrethans.nl/feed-phpinternalsnews.xml, you can download this episode's MP3 file, and it's available on Spotify and iTunes. There is a dedicated website: https://phpinternals.news
Transcript
- Derick Rethans 0:14
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Hi, I'm Derick. Welcome to PHP internals news, a podcast dedicated to explaining the latest developments in the PHP language. This is Episode 90. Today I'm talking with Nikita Popov about the read only properties version two RFC that he's proposing. Nikita, would you please introduce yourself?
- Nikita Popov 0:33
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Hi, Derick. I'm Nikita and I do PHP core development work by JetBrains.
- Derick Rethans 0:39
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What does this RFC proposing?
- Nikita Popov 0:41
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This RFC is proposing read only properties, which means that the property can only be initialized once and then not changed afterwards. Again, the idea here is that since PHP 7.4, we have typed properties. A remaining problem with them is that people are not confident making public type properties because they still ensure that the type is correct, but they might not be upholding other invariants. For example, if you have some, like additional checks in your constructor, that string property is actually a non empty string property, then you might not want to make it public because then it could be modified to an empty value for example. One nowadays fairly common case is where properties are actually only initialized in the constructor and not changed afterwards any more. So I think this kind of mutable object pattern is becoming more and more popular in PHP.
- Derick Rethans 1:35
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You mean the immutable object?
- Nikita Popov 1:37
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Sorry, immutable. And read only properties address that case. So you can simply put a public read only typed property in your class, and then it can be initialized once in the constructor and you can be... You don't have to be afraid that someone outside the class is going to modify it afterwards. That's the basic premise of this RFC.
- Derick Rethans 1:57
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But it also means that objects of the class itself can modify that value any more, either.
- Nikita Popov 2:01
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Exactly. So that's, I think, a
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