language/oop5/interfaces.xml
3d522c890d98c563bb283cf89ec5da5f535cfb8f
3d522c890d98c563bb283cf89ec5da5f535cfb8f
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@@ -58,12 +58,6 @@
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</para>
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<warning>
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<para>
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A class can implement two interfaces which define a method with the
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same name, only if the method declaration in both interfaces is identical.
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</para>
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</warning>
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<warning>
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<para>
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A class that implements an interface may use a different name for its parameters than
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the interface. However, as of PHP 8.0 the language supports <link linkend="functions.named-arguments">named arguments</link>, which means
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callers may rely on the parameter name in the interface. For that reason, it is strongly
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@@ -79,17 +73,20 @@
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<note>
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<para>
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The class implementing the interface must declare all methods in the interface
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with a <link linkend="language.oop.lsp">compatible signature</link>.
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with a <link linkend="language.oop.lsp">compatible signature</link>. A class can implement multiple interfaces
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which declare a method with the same name. In this case, the implementation must follow the
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<link linkend="language.oop.lsp">signature compatibility rules</link> for all the interfaces. So
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<link linkend="language.oop5.variance">covariance and contravariance</link> can be applied.
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</para>
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</note>
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</sect2>
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<!-- Move this to OOP constants page? -->
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<sect2 xml:id="language.oop5.interfaces.constants">
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<title><literal>Constants</literal></title>
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<title>Constants</title>
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<para>
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It's possible for interfaces to have constants. Interface constants work exactly
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like <link linkend="language.oop5.constants">class constants</link> except
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they cannot be overridden by a class/interface that inherits them.
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like <link linkend="language.oop5.constants">class constants</link>.
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Prior to PHP 8.1.0, they cannot be overridden by a class/interface that inherits them.
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</para>
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</sect2>
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<sect2 xml:id="language.oop5.interfaces.examples">
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@@ -186,6 +183,33 @@ class D implements B
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]]>
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</programlisting>
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</example>
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<example xml:id="language.oop5.interfaces.examples.variance.multiple.interfaces">
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<title>Variance compatibility with multiple interfaces</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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class Foo {}
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class Bar extends Foo {}
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interface A {
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public function myfunc(Foo $arg): Foo;
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}
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interface B {
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public function myfunc(Bar $arg): Bar;
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}
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class MyClass implements A, B
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{
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public function myfunc(Foo $arg): Bar
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{
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return new Bar();
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}
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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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<example xml:id="language.oop5.interfaces.examples.ex3">
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<title>Multiple interface inheritance</title>
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<programlisting role="php">
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echo A::B;
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// This will however not work because it's not allowed to
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// override constants.
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class B implements A
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{
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const B = 'Class constant';
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}
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// Prints: Class constant
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// Prior to PHP 8.1.0, this will however not work because it was not
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// allowed to override constants.
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echo B::B;
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?>
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]]>
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</programlisting>
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// Classes that extend the abstract class must implement the rest.
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abstract class B implements A
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{
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pubic function foo(string $s): string
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public function foo(string $s): string
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{
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return $s . PHP_EOL;
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}
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