language.oop5.visibility.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html> <head> <title>Visibility</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head> <body><div style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="language.oop5.decon.html">Constructors and Destructors</a></div> <div class="next" style="text-align: right; float: right;"><a href="language.oop5.paamayim-nekudotayim.html">Scope Resolution Operator (::)</a></div> <div class="up"><a href="language.oop5.html">Classes and Objects (PHP 5)</a></div> <div class="home"><a href="index.html">PHP Manual</a></div></div><hr /><div id="language.oop5.visibility" class="sect1"> <h2 class="title">Visibility</h2> <p class="para"> The visibility of a property or method can be defined by prefixing the declaration with the keywords: public, protected or private. Public declared items can be accessed everywhere. Protected limits access to inherited and parent classes (and to the class that defines the item). Private limits visibility only to the class that defines the item. </p> <div id="language.oop5.visiblity-members" class="sect2"> <h3 class="title">Members Visibility</h3> <p class="para"> Class members must be defined with public, private, or protected. </p> <p class="para"> <div class="example"> <p><b>Example #1 Member declaration</b></p> <div class="example-contents"><div class="phpcode"><code><span style="color: #000000"><span style="color: #0000BB"><?php<br /></span><span style="color: #FF8000">/**<br /> * Define MyClass<br /> */<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">MyClass<br /></span><span style="color: #007700">{<br /> public </span><span style="color: #0000BB">$public </span><span style="color: #007700">= </span><span style="color: #DD0000">'Public'</span><span style="color: #007700">;<br /> protected </span><span style="color: #0000BB">$protected </span><span style="color: #007700">= </span><span style="color: #DD0000">'Protected'</span><span style="color: #007700">;<br /> private </span><span style="color: #0000BB">$private </span><span style="color: #007700">= </span><span style="color: #DD0000">'Private'</span><span style="color: #007700">;<br /><br /> function </span><span style="color: #0000BB">printHello</span><span style="color: #007700">()<br /> {<br /> echo </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">public</span><span style="color: #007700">;<br /> echo </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">protected</span><span style="color: #007700">;<br /> echo </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">private</span><span style="color: #007700">;<br /> }<br />}<br /><br /></span><span style="color: #0000BB">$obj </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass</span><span style="color: #007700">();<br />echo </span><span style="color: #0000BB">$obj</span><span style="color: #007700">-></span><span style="color: #0000BB">public</span><span style="color: #007700">; </span><span style="color: #FF8000">// Works<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$obj</span><span style="color: #007700">-></span><span style="color: #0000BB">protected</span><span style="color: #007700">; </span><span style="color: #FF8000">// Fatal Error<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$obj</span><span style="color: #007700">-></span><span style="color: #0000BB">private</span><span style="color: #007700">; </span><span style="color: #FF8000">// Fatal Error<br /></span><span style="color: #0000BB">$obj</span><span style="color: #007700">-></span><span style="color: #0000BB">printHello</span><span style="color: #007700">(); </span><span style="color: #FF8000">// Shows Public, Protected and Private<br /><br /><br />/**<br /> * Define MyClass2<br /> */<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">MyClass2 </span><span style="color: #007700">extends </span><span style="color: #0000BB">MyClass<br /></span><span style="color: #007700">{<br /> </span><span style="color: #FF8000">// We can redeclare the public and protected method, but not private<br /> </span><span style="color: #007700">protected </span><span style="color: #0000BB">$protected </span><span style="color: #007700">= </span><span style="color: #DD0000">'Protected2'</span><span style="color: #007700">;<br /><br /> function </span><span style="color: #0000BB">printHello</span><span style="color: #007700">()<br /> {<br /> echo </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">public</span><span style="color: #007700">;<br /> echo </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">protected</span><span style="color: #007700">;<br /> echo </span><span style="color: #0000BB">$this</span><span style="color: #007700">-></span><span style="color: #0000BB">private</span><span style="color: #007700">;<br /> }<br />}<br /><br /></span><span style="color: #0000BB">$obj2 </span><span style="color: #007700">= new </span><span style="color: #0000BB">MyClass2</span><span style="color: #007700">();<br />echo </span><span style="color: #0000BB">$obj2</span><span style="color: #007700">-></span><span style="color: #0000BB">public</span><span style="color: #007700">; </span><span style="color: #FF8000">// Works<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$obj2</span><span style="color: #007700">-></span><span style="color: #0000BB">private</span><span style="color: #007700">; </span><span style="color: #FF8000">// Undefined<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">$obj2</span><span style="color: #007700">-></span><span style="color: #0000BB">protected</span><span style="color: #007700">; </span><span style="color: #FF8000">// Fatal Error<br /></span><span style="color: #0000BB">$obj2</span><span style="color: #007700">-></span><span style="color: #0000BB">printHello</span><span style="color: #007700">(); </span><span style="color: #FF8000">// Shows Public, Protected2, Undefined<br /><br /></span><span style="color: #0000BB">?></span></span></code></div> </div> </div>⌨️ 快捷键说明
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