language/oop5/visibility.xml
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f5e5b54129045a7d02c5285a88cea0abff8ffb6f
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<sect1 xml:id="language.oop5.visibility" xmlns="http://docbook.org/ns/docbook">
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<title>Visibility</title>
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<para>
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The visibility of a property or method can be defined by prefixing
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the declaration with the keywords <emphasis>public</emphasis>,
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<emphasis>protected</emphasis> or
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<emphasis>private</emphasis>. Class members declared public can be
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The visibility of a property, a method or (as of PHP 7.1.0) a constant can be defined by prefixing
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the declaration with the keywords <literal>public</literal>,
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<literal>protected</literal> or
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<literal>private</literal>. Class members declared public can be
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accessed everywhere. Members declared protected can be accessed
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only within the class itself and by inherited classes. Members
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declared as private may only be accessed by the class that defines
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the member.
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only within the class itself and by inheriting and parent
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classes. Members declared as private may only be accessed by the
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class that defines the member.
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</para>
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<sect2 xml:id="language.oop5.visibility-members">
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<title>Property Visibility</title>
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<para>
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Class properties must be defined as public, private, or
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protected. If declared using <emphasis>var</emphasis>,
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the property will be defined as public.
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Class properties may be defined as public, private, or
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protected. Properties declared without any explicit visibility
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keyword are defined as public.
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</para>
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<para>
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<example>
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*/
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class MyClass2 extends MyClass
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{
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// We can redeclare the public and protected method, but not private
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// We can redeclare the public and protected properties, but not private
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public $public = 'Public2';
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protected $protected = 'Protected2';
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function printHello()
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echo $obj2->public; // Works
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echo $obj2->protected; // Fatal Error
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echo $obj2->private; // Undefined
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$obj2->printHello(); // Shows Public, Protected2, Undefined
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$obj2->printHello(); // Shows Public2, Protected2, Undefined
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?>
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]]>
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</programlisting>
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</example>
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</para>
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<note>
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<simpara>
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The PHP 4 method of declaring a variable with the
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<emphasis>var</emphasis> keyword is still supported for compatibility
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reasons (as a synonym for the public keyword). In PHP 5 before 5.1.3, its
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usage would generate an <constant>E_STRICT</constant> warning.
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</simpara>
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</note>
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</sect2>
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<sect2 xml:id="language.oop5.visiblity-methods">
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</para>
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</sect2>
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<sect2 xml:id="language.oop5.visiblity-constants">
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<title>Constant Visibility</title>
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<para>
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As of PHP 7.1.0, class constants may be defined as public, private, or
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protected. Constants declared without any explicit visibility
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keyword are defined as public.
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</para>
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<para>
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<example>
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<title>Constant Declaration as of PHP 7.1.0</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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/**
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* Define MyClass
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*/
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class MyClass
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{
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// Declare a public constant
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public const MY_PUBLIC = 'public';
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// Declare a protected constant
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protected const MY_PROTECTED = 'protected';
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// Declare a private constant
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private const MY_PRIVATE = 'private';
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public function foo()
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{
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echo self::MY_PUBLIC;
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echo self::MY_PROTECTED;
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echo self::MY_PRIVATE;
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}
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}
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$myclass = new MyClass();
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MyClass::MY_PUBLIC; // Works
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MyClass::MY_PROTECTED; // Fatal Error
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MyClass::MY_PRIVATE; // Fatal Error
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$myclass->foo(); // Public, Protected and Private work
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/**
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* Define MyClass2
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*/
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class MyClass2 extends MyClass
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{
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// This is public
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function foo2()
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{
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echo self::MY_PUBLIC;
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echo self::MY_PROTECTED;
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echo self::MY_PRIVATE; // Fatal Error
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}
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}
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$myclass2 = new MyClass2;
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echo MyClass2::MY_PUBLIC; // Works
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$myclass2->foo2(); // Public and Protected work, not Private
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?>
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]]>
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</programlisting>
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</example>
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</para>
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</sect2>
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<sect2 xml:id="language.oop5.visibility-other-objects">
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<title>Visibility from other objects</title>
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<para>
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</example>
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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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