# Ability to assign new object to a class property. - Thread: https://externals.io/message/59902 - Original archive: https://news-web.php.net/php.internals/59902 - Started by Dmitri Snytkine on 2012-04-13T19:19:28+00:00 - Messages: 13 - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #59902 — Dmitri Snytkine — 2012-04-13T19:19:28+00:00 URL: https://externals.io/message/59902#59902 I always wondered why can't we do something like this in php class MyClass{ private $storage = new ArrayObject(); public function __construct($v){ // whatever } // rest of class } Why can't we create a new object and assign it to property like this? Then when a new instance of MyClass is created the $storage variable is automatically assigned a new ArrayObject. Somethink like this is valid, possible and commonly used in Java, why not in php? Has anyone already asked for this to be valid syntax in php? Dmitri Snytkine Web Developer Ultra Logistics, Inc. Phone: (888) 220-4640 x 2097 Fax: (888) 795-6642 E-Mail: dsnytkine@ultralogistics.com Web: www.ultralogistics.com "A Top 100 Logistics I.T. Provider in 2011" --- ## #59903 — Etienne Kneuss — 2012-04-13T19:26:51+00:00 URL: https://externals.io/message/59902#59903 · In reply to: #59902 Hi, On Fri, Apr 13, 2012 at 21:19, Dmitri Snytkine wrote: > I always wondered why can't we do something like this in php > > class MyClass{ > > private $storage = new ArrayObject(); > > public function __construct($v){ > // whatever > } > > // rest of class > > } > > Why can't we create a new object and assign it to property like this? > > Then when a new instance of MyClass is created the $storage variable is > automatically assigned a new ArrayObject. > Somethink like this is valid, possible and commonly used in Java, why not in > php? > > Has anyone already asked for this to be valid syntax in php? Sure, people have asked for that. It is definitely possible in theory, but requires quite some work: It requires to add an initialization phase to the class. In other languages, it is typically done by automatically adding the initialization code in the constructors. We cannot do that in PHP because calling parent constructors is not mandatory. In other words, in order to allow for this, we need to add an initialization phase before calling the constructors. Allowing this syntax for classes properties would also require adding an initialization phase, and it is not entirely clear when to run it (i.e. when the class is first used or when it is loaded). Best, > > Dmitri Snytkine > Web Developer > Ultra Logistics, Inc. > Phone: (888) 220-4640 x 2097 > Fax: (888) 795-6642 > E-Mail: dsnytkine@ultralogistics.com > Web: www.ultralogistics.com > > "A Top 100 Logistics I.T. Provider in 2011" > > > > > -- > > > -- Etienne Kneuss http://www.colder.ch --- ## #59904 — Dmitri Snytkine — 2012-04-13T19:29:30+00:00 URL: https://externals.io/message/59902#59904 But why is it possible to assing a new array to a property like that but not a new instance of some class? Isn't a new array also requires some type of initialization? Dmitri Snytkine Web Developer Ultra Logistics, Inc. Phone: (888) 220-4640 x 2097 Fax: (888) 795-6642 E-Mail: dsnytkine@ultralogistics.com Web: www.ultralogistics.com "A Top 100 Logistics I.T. Provider in 2011" -----Original Message----- From: ekneuss@gmail.com [mailto:ekneuss@gmail.com] On Behalf Of Etienne Kneuss Sent: Friday, April 13, 2012 3:27 PM To: Dmitri Snytkine Cc: PHP Internals Subject: Re: [PHP-DEV] Ability to assign new object to a class property. Hi, On Fri, Apr 13, 2012 at 21:19, Dmitri Snytkine wrote: > I always wondered why can't we do something like this in php > > class MyClass{ > > private $storage = new ArrayObject(); > > public function __construct($v){ > // whatever > } > > // rest of class > > } > > Why can't we create a new object and assign it to property like this? > > Then when a new instance of MyClass is created the $storage variable is > automatically assigned a new ArrayObject. > Somethink like this is valid, possible and commonly used in Java, why not in > php? > > Has anyone already asked for this to be valid syntax in php? Sure, people have asked for that. It is definitely possible in theory, but requires quite some work: It requires to add an initialization phase to the class. In other languages, it is typically done by automatically adding the initialization code in the constructors. We cannot do that in PHP because calling parent constructors is not mandatory. In other words, in order to allow for this, we need to add an initialization phase before calling the constructors. Allowing this syntax for classes properties would also require adding an initialization phase, and it is not entirely clear when to run it (i.e. when the class is first used or when it is loaded). Best, > > Dmitri Snytkine > Web Developer > Ultra Logistics, Inc. > Phone: (888) 220-4640 x 2097 > Fax: (888) 795-6642 > E-Mail: dsnytkine@ultralogistics.com > Web: www.ultralogistics.com > > "A Top 100 Logistics I.T. Provider in 2011" > > > > > -- > > > -- Etienne Kneuss http://www.colder.ch --- ## #59905 — Etienne Kneuss — 2012-04-13T19:36:02+00:00 URL: https://externals.io/message/59902#59905 · In reply to: #59904 On Fri, Apr 13, 2012 at 21:29, Dmitri Snytkine wrote: > But why is it possible to assing  a new array to a property like that but not a new instance of some class? > Isn't a new array also requires some type of initialization? Only static values are allowed, which means that the value requires no code to execute. > > Dmitri Snytkine > Web Developer > Ultra Logistics, Inc. > Phone: (888) 220-4640 x 2097 > Fax: (888) 795-6642 > E-Mail: dsnytkine@ultralogistics.com > Web: www.ultralogistics.com > > "A Top 100 Logistics I.T. Provider in 2011" > > > -----Original Message----- > From: ekneuss@gmail.com [mailto:ekneuss@gmail.com] On Behalf Of Etienne Kneuss > Sent: Friday, April 13, 2012 3:27 PM > To: Dmitri Snytkine > Cc: PHP Internals > Subject: Re: [PHP-DEV] Ability to assign new object to a class property. > > Hi, > > On Fri, Apr 13, 2012 at 21:19, Dmitri Snytkine > wrote: > > […] > > Sure, people have asked for that. It is definitely possible in theory, > but requires quite some work: > > It requires to add an initialization phase to the class. In other > languages, it is typically done by automatically adding the > initialization code in the constructors. We cannot do that in PHP > because calling parent constructors is not mandatory. > > In other words, in order to allow for this, we need to add an > initialization phase before calling the constructors. > > Allowing this syntax for classes properties would also require adding > an initialization phase, and it is not entirely clear when to run it > (i.e. when the class is first used or when it is loaded). > > Best, > > > […] > > > > -- > Etienne Kneuss > http://www.colder.ch > -- Etienne Kneuss http://www.colder.ch --- ## #59912 — Stas Malyshev — 2012-04-13T20:06:30+00:00 URL: https://externals.io/message/59902#59912 · In reply to: #59902 Hi! > Why can't we create a new object and assign it to property like this? Because the engine doesn't run code when parsing class definitions so defaults should be constants (otherwise would also create a lot of trouble for bytecode caching as object are not cacheable). Use ctor for complex initializations. -- Stanislav Malyshev, Software Architect SugarCRM: http://www.sugarcrm.com/ (408)454-6900 ext. 227 --- ## #59915 — Anthony Ferrara — 2012-04-13T21:27:32+00:00 URL: https://externals.io/message/59902#59915 · In reply to: #59912 Stas, > Because the engine doesn't run code when parsing class definitions so > defaults should be constants (otherwise would also create a lot of > trouble for bytecode caching as object are not cacheable). Just throwing this out there, but that code wouldn't be run on parse. It would be "queued" to run prior to the constructor on instantiation. So then, we should be able to execute that code inside of _object_and_properties_init... Then, all you'd need to do is add a single field to _zend_property_info to indicate it should be a class instantiation. From there, you'd want a flag on zend_class_entry to indicate if it has any dynamic properties. So the work flow would be that in _object_and_properties_init, when it copies the hash table, check the flag on the zce. If true, iterate over the properties to check for instantiation, and if so, do it. This would (in theory) be able to support almost any type of dynamic code in the property declaration, as long as it doesn't reference `$this` (which would still be undefined at that point). So you could do: protected $foo = "bar" . BAZ; protected $fiz = new Biz(new Baz, array(123)); Just a thought... Anthony > Hi! > > > […] > > Because the engine doesn't run code when parsing class definitions so > defaults should be constants (otherwise would also create a lot of > trouble for bytecode caching as object are not cacheable). > > Use ctor for complex initializations. > > -- > Stanislav Malyshev, Software Architect > SugarCRM: http://www.sugarcrm.com/ > (408)454-6900 ext. 227 --- ## #59921 — Stas Malyshev — 2012-04-14T00:07:55+00:00 URL: https://externals.io/message/59902#59921 · In reply to: #59915 Hi! > Just throwing this out there, but that code wouldn't be run on parse. > It would be "queued" to run prior to the constructor on instantiation. Why? You have perfectly good ctor, why not use it? -- Stanislav Malyshev, Software Architect SugarCRM: http://www.sugarcrm.com/ (408)454-6900 ext. 227 --- ## #59925 — Dmitri Snytkine — 2012-04-14T12:03:07+00:00 URL: https://externals.io/message/59902#59925 Why not? It's convenient to assign an empty array to a property in this manner. private $storage = array(); So why not private $storage = new ArrayObject(); Doing stuff like this in class definition vs in constructor just makes code look cleaner. Dmitri Snytkine Web Developer Ultra Logistics, Inc. Phone: (888) 220-4640 x 2097 Fax: (888) 795-6642 E-Mail: dsnytkine@ultralogistics.com Web: www.ultralogistics.com "A Top 100 Logistics I.T. Provider in 2011" -----Original Message----- From: Stas Malyshev [mailto:smalyshev@sugarcrm.com] Sent: Friday, April 13, 2012 8:08 PM To: Anthony Ferrara Cc: Dmitri Snytkine; PHP Internals Subject: Re: [PHP-DEV] Ability to assign new object to a class property. Hi! > Just throwing this out there, but that code wouldn't be run on parse. > It would be "queued" to run prior to the constructor on instantiation. Why? You have perfectly good ctor, why not use it? -- Stanislav Malyshev, Software Architect SugarCRM: http://www.sugarcrm.com/ (408)454-6900 ext. 227 --- ## #59934 — Stas Malyshev — 2012-04-14T20:37:25+00:00 URL: https://externals.io/message/59902#59934 · In reply to: #59925 Hi! > It's convenient to assign an empty array to a property in this manner. > > private $storage = array(); > > So why not > private $storage = new ArrayObject(); array is a static constant. Objects have complex behavior. So it's better to handle this in ctor. I see no value in splitting ctor into multiple pieces, and debugging such thing would be a nightmare. -- Stanislav Malyshev, Software Architect SugarCRM: http://www.sugarcrm.com/ (408)454-6900 ext. 227 --- ## #59972 — Simon Schick — 2012-04-15T22:47:26+00:00 URL: https://externals.io/message/59902#59972 · In reply to: #59902 2012/4/13 Dmitri Snytkine : > I always wondered why can't we do something like this in php > > class MyClass{ > > private $storage = new ArrayObject(); > > public function __construct($v){ > // whatever > } > > // rest of class > > } > > Why can't we create a new object and assign it to property like this? > > Then when a new instance of MyClass is created the $storage variable is > automatically assigned a new ArrayObject. > Somethink like this is valid, possible and commonly used in Java, why not in > php? > > Has anyone already asked for this to be valid syntax in php? > > Dmitri Snytkine > Web Developer > Ultra Logistics, Inc. > Phone: (888) 220-4640 x 2097 > Fax: (888) 795-6642 > E-Mail: dsnytkine@ultralogistics.com > Web: www.ultralogistics.com > > "A Top 100 Logistics I.T. Provider in 2011" > > > > > -- > > > Hi, Dmitri Just to add a random thought .... When do you expect this code to be executed? class Foo { static public $foo = new StdClass(); } Sorry if this code contains syntax-errors, but I think you'll still get the point ;) Bye Simon --- ## #60005 — Dmitri Snytkine — 2012-04-16T15:29:52+00:00 URL: https://externals.io/message/59902#60005 In my example the property was not static. To make it clear - it cannot be static for this to work. The instance of the class assigned to a property will be created when the object is created -most likely it will have to be done before the constructor is called so that the instance of property is available to constructor. Dmitri Snytkine Web Developer Ultra Logistics, Inc. Phone: (888) 220-4640 x 2097 Fax: (888) 795-6642 E-Mail: dsnytkine@ultralogistics.com Web: www.ultralogistics.com "A Top 100 Logistics I.T. Provider in 2011" -----Original Message----- From: Simon Schick [mailto:simonsimcity@googlemail.com] Sent: Sunday, April 15, 2012 6:47 PM To: Dmitri Snytkine Cc: PHP Internals Subject: Re: [PHP-DEV] Ability to assign new object to a class property. 2012/4/13 Dmitri Snytkine : > I always wondered why can't we do something like this in php > > class MyClass{ > > private $storage = new ArrayObject(); > > public function __construct($v){ > // whatever > } > > // rest of class > > } > > Why can't we create a new object and assign it to property like this? > > Then when a new instance of MyClass is created the $storage variable is > automatically assigned a new ArrayObject. > Somethink like this is valid, possible and commonly used in Java, why not in > php? > > Has anyone already asked for this to be valid syntax in php? > > Dmitri Snytkine > Web Developer > Ultra Logistics, Inc. > Phone: (888) 220-4640 x 2097 > Fax: (888) 795-6642 > E-Mail: dsnytkine@ultralogistics.com > Web: www.ultralogistics.com > > "A Top 100 Logistics I.T. Provider in 2011" > > > > > -- > > > Hi, Dmitri Just to add a random thought .... When do you expect this code to be executed? class Foo { static public $foo = new StdClass(); } Sorry if this code contains syntax-errors, but I think you'll still get the point ;) Bye Simon --- ## #60203 — Richard Lynch — 2012-04-18T21:31:11+00:00 URL: https://externals.io/message/59902#60203 · In reply to: #59972 > Just to add a random thought .... > When do you expect this code to be executed? > > class Foo { > static public $foo = new StdClass(); > } I may be too late to this party, but... For what it's worth, if the non-scalar initialization in class definition were to be implemented, I, the naive PHP developer, would expect the implementation to execute the new StdClass() exactly once (either at compile time or on the instantiation of the first instance) and Foo::$foo or whatever it is would be static in the sense that the same instance of a stdClass would be shared by all Foo instances. I'm with Stas on this one though. Yes, it would be nifty syntactic sugar, and I used to yearn for it. But complex initializations in the constructor is something I've grown used to, and now appreciate as a Feature. Trying to find all the little bits and pieces of non-scalar initializations up and down the chain of a complex class hierarchy is already difficult enough. Tossing in a bunch more places it can happen is Not Good (tm). -- brain cancer update: http://richardlynch.blogspot.com/search/label/brain%20tumor Donate: https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=FS9NLTNEEKWBE --- ## #60212 — Arvids Godjuks — 2012-04-19T08:26:52+00:00 URL: https://externals.io/message/59902#60212 · In reply to: #60203 I have to agree with Richard as a user-land developer. It looks nice, but knowing how people can twist things I don't think I would like this feature get implemented. It just add stuff that is crazy to debug. Consider someone adds a property and initializes a user-land object. That object has other object properties with are created and the chain goes on for 2-3 more levels. Dealing with a __construct or a dedicated init method is far easier and at least predictable stuff. I imagine someone initiating objects at property declaration and then somewhere in the code assigning the data they want the object to work with instead of just passing it in to the constructor or calling a dedicated method to do that right after creating an object. 19 апреля 2012 г. 0:31 пользователь Richard Lynch написал: > > > […] > > I may be too late to this party, but... > > For what it's worth, if the non-scalar initialization in class > definition were to be implemented, I, the naive PHP developer, would > expect the implementation to execute the new StdClass() exactly once > (either at compile time or on the instantiation of the first instance) > and Foo::$foo or whatever it is would be static in the sense that the > same instance of a stdClass would be shared by all Foo instances. > > I'm with Stas on this one though. > > Yes, it would be nifty syntactic sugar, and I used to yearn for it. > > But complex initializations in the constructor is something I've grown > used to, and now appreciate as a Feature. > > Trying to find all the little bits and pieces of non-scalar > initializations up and down the chain of a complex class hierarchy is > already difficult enough. > > Tossing in a bunch more places it can happen is Not Good (tm). > > -- > brain cancer update: > http://richardlynch.blogspot.com/search/label/brain%20tumor > Donate: > > https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=FS9NLTNEEKWBE