language/oop5/decon.xml
9f351a14a749721a74df1dc6ac9533cf796a652e
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@@ -61,10 +61,10 @@ $obj = new OtherSubClass();
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</programlisting>
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</example>
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<para>
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Unlike with other methods, PHP will not generate an
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<constant>E_STRICT</constant> level error message when
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<link linkend="object.construct">__construct()</link> is overridden with different parameters
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than the parent <link linkend="object.construct">__construct()</link> method has.
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Unlike other methods, <link linkend="object.construct">__construct()</link>
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is exempt from the usual
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<link linkend="language.oop.lsp">signature compatibility rules</link>
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when being extended.
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</para>
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<para>
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Constructors are ordinary methods which are called during the instantiation of their
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@@ -138,7 +138,7 @@ class Point {
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</programlisting>
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</example>
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<para>
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When a constructor argument includes a visibility modifier, PHP will interpret it as
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When a constructor argument includes a modifier, PHP will interpret it as
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both an object property and a constructor argument, and assign the argument value to
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the property. The constructor body may then be empty or may contain other statements.
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Any additional statements will be executed after the argument values have been assigned
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@@ -150,6 +150,13 @@ class Point {
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</para>
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<note>
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<para>
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Using a <link linkend="language.oop5.visibility">visibility modifier</link> (<literal>public</literal>,
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<literal>protected</literal> or <literal>private</literal>) is the most likely way to apply property
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promotion, but any other single modifier (such as <literal>readonly</literal>) will have the same effect.
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</para>
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</note>
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<note>
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<para>
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Object properties may not be typed <type>callable</type> due to engine ambiguity that would
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introduce. Promoted arguments, therefore, may not be typed <type>callable</type> either. Any
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other <link linkend="language.types.declarations">type declaration</link> is permitted, however.
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@@ -157,12 +164,66 @@ class Point {
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</note>
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<note>
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<para>
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<!-- This should be linked once attributes are documented. -->
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Attributes placed on a promoted constructor argument will be replicated to both the property
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and argument.
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As promoted properties are desugared to both a property as well as a function parameter, any
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and all naming restrictions for both properties as well as parameters apply.
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</para>
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</note>
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<note>
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<para>
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<link linkend="language.attributes">Attributes</link> placed on a
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promoted constructor argument will be replicated to both the property
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and argument. Default values on a promoted constructor argument will be replicated only to the argument and not the property.
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</para>
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</note>
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</sect3>
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<sect3 xml:id="language.oop5.decon.constructor.new">
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<title>New in initializers</title>
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<para>
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As of PHP 8.1.0, objects can be used as default parameter values,
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static variables, and global constants, as well as in attribute arguments.
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Objects can also be passed to <function>define</function> now.
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</para>
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<note>
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<para>
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The use of a dynamic or non-string class name or an anonymous class is not allowed.
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The use of argument unpacking is not allowed.
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The use of unsupported expressions as arguments is not allowed.
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</para>
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</note>
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<example>
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<title>Using new in initializers</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// All allowed:
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static $x = new Foo;
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const C = new Foo;
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function test($param = new Foo) {}
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#[AnAttribute(new Foo)]
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class Test {
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public function __construct(
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public $prop = new Foo,
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) {}
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}
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// All not allowed (compile-time error):
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function test(
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$a = new (CLASS_NAME_CONSTANT)(), // dynamic class name
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$b = new class {}, // anonymous class
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$c = new A(...[]), // argument unpacking
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$d = new B($abc), // unsupported constant expression
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) {}
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?>
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]]>
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</programlisting>
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</example>
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</sect3>
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<sect3 xml:id="language.oop5.decon.constructor.static">
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<title>Static creation methods</title>
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<para>
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@@ -191,12 +252,12 @@ class Product {
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}
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public static function fromJson(string $json): static {
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$data = json_decode($json);
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$data = json_decode($json, true);
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return new static($data['id'], $data['name']);
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}
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public static function fromXml(string $xml): static {
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// Put your own logic here.
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// Custom logic here.
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$data = convert_xml_to_array($xml);
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$new = new static();
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$new->id = $data['id'];
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@@ -213,10 +274,10 @@ $p3 = Product::fromXml($some_xml_string);
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</example>
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<para>
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The constructor may be made private or protected to prevent it from being called externally.
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If so, only a static method will be able to instantiate the class. Because they are in the
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If so, only a static method will be able to instantiate the class. Because they are in the
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same class definition they have access to private methods, even if not of the same object
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instance. The private constructor is optional and may or may not make sense depending on
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the use case..
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instance. The private constructor is optional and may or may not make sense depending on
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the use case.
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</para>
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<para>
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The three public static methods then demonstrate different ways of instantiating the object.
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<void />
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</methodsynopsis>
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<para>
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PHP 5 introduces a destructor concept similar to that of other
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PHP possesses a destructor concept similar to that of other
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object-oriented languages, such as C++. The destructor method will be
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called as soon as there are no other references to a particular object,
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or in any order during the shutdown sequence.
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</sect2>
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</sect1>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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