php-doc-en/language/oop5/visibility.xml

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 <sect1 id="language.oop5.visibility">
  <title>Visibility</title>
  <para>
  The visibility of a member or method can be defined by prefixing the
  declaration with the keywords: public, protected or private. Public  
  declared items can be allow access to any caller.  Protected limits access
  access to only classes inherited. Protected limits visiblity only to the
  class that defines the item.
  </para>
  <sect2 id="language.oop5.visiblity-members">
   <title>Members Visibility</title>
   <para>
   Class members must be defined with public, private, or protected.
   </para>
    <example>
     <title>Member declaration</title>
     <programlisting role="php">
<![CDATA[
<?php

class MyClass {
   public    $public     = "MyClass::public!\n";
   protected $protected  = "MyClass::Protected!\n";
   protected $protected2 = "MyClass::Protected2!\n";
   private   $private    = "MyClass::private!\n";

   function printHello() {
      print "MyClass::printHello() " . $this->private;
      print "MyClass::printHello() " . $this->protected;
      print "MyClass::printHello() " . $this->protected2;
   }
}

class MyClass2 extends MyClass {
   protected $protected = "MyClass2::protected!\n";

   function printHello() {

      MyClass::printHello();    

      print "MyClass2::printHello() " . $this->public; 
      print "MyClass2::printHello() " . $this->protected; 
      print "MyClass2::printHello() " . $this->protected2;

      /* Will result in a Fatal Error: */
      //print "MyClass2::printHello() " . $this->private; /* Fatal Error */

   }
}

$obj = new MyClass();

print "Main:: " . $obj->public;
//print $obj->private; /* Fatal Error */
//print $obj->protected;  /* Fatal Error */
//print $obj->protected2;  /* Fatal Error */

$obj->printHello(); /* Should print */

$obj2 = new MyClass2();
print "Main:: " . $obj2->private; /* Undefined */ 

//print $obj2->protected;   /* Fatal Error */ 
//print $obj2->protected2;  /* Fatal Error */ 

$obj2->printHello();
?> 
]]>
     </programlisting>
    </example>
   <note>
    <simpara>
     The use PHP 4 use of declaring a variable with the keyword 'var' is
     no longer valid for PHP 5 objects. For compatiblity a variable declared
     in php will be assumed with public visiblity, and a E_STRICT warning will
     be issued.
    </simpara>
   </note>
  </sect2>
  <sect2 id="language.oop5.visiblity-methods">
   <title>Method Visibility</title>
   <para>
    .
   </para>
  </sect2>


 </sect1>
 
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