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Source of: /manual/en/language.oop5.references.php

<?php
include_once $_SERVER['DOCUMENT_ROOT'] . '/include/shared-manual.inc';
$TOC = array();
$PARENTS = array();
include_once dirname(__FILE__) ."/toc/language.oop5.inc";
$setup = array (
  'home' =>
  array (
    0 => 'index.php',
    1 => 'PHP Manual',
  ),
  'head' =>
  array (
    0 => 'UTF-8',
    1 => 'en',
  ),
  'this' =>
  array (
    0 => 'language.oop5.references.php',
    1 => 'Objects and references',
  ),
  'up' =>
  array (
    0 => 'language.oop5.php',
    1 => 'Classes and Objects',
  ),
  'prev' =>
  array (
    0 => 'language.oop5.late-static-bindings.php',
    1 => 'Late Static Bindings',
  ),
  'next' =>
  array (
    0 => 'language.oop5.serialization.php',
    1 => 'Object Serialization',
  ),
);
$setup["toc"] = $TOC;
$setup["parents"] = $PARENTS;
manual_setup($setup);

manual_header();
?>
<div id="language.oop5.references" class="sect1">
  <h2 class="title">Objects and references</h2>
  <p class="para">
   One of the key-points of PHP5 OOP that is often mentioned is that
   &quot;objects are passed by references by default&quot;. This is not completely true.
   This section rectifies that general thought using some examples.
  </p>

  <p class="para">
   A PHP reference is an alias, which allows two different variables to write
   to the same value. As of PHP5, an object variable doesn&#039;t contain the object
   itself as value anymore. It only contains an object identifier which allows
   object accessors to find the actual object. When an object is sent by
   argument, returned or assigned to another variable, the different variables
   are not aliases: they hold a copy of the identifier, which points to the same
   object.
  </p>

  <div class="example">
   <p><b>Example #1 References and Objects</b></p>
   <div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">class&nbsp;</span><span style="color: #0000BB">A&nbsp;</span><span style="color: #007700">{<br />&nbsp;&nbsp;&nbsp;&nbsp;public&nbsp;</span><span style="color: #0000BB">$foo&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">;<br />}&nbsp;&nbsp;<br /><br /></span><span style="color: #0000BB">$a&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">A</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$a</span><span style="color: #007700">;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;$a&nbsp;and&nbsp;$b&nbsp;are&nbsp;copies&nbsp;of&nbsp;the&nbsp;same&nbsp;identifier<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;($a)&nbsp;=&nbsp;($b)&nbsp;=&nbsp;&lt;id&gt;<br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">foo&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">;<br />echo&nbsp;</span><span style="color: #0000BB">$a</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">foo</span><span style="color: #007700">.</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /><br /></span><span style="color: #0000BB">$c&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">A</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$d&nbsp;</span><span style="color: #007700">=&nbsp;&amp;</span><span style="color: #0000BB">$c</span><span style="color: #007700">;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;$c&nbsp;and&nbsp;$d&nbsp;are&nbsp;references<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//&nbsp;($c,$d)&nbsp;=&nbsp;&lt;id&gt;<br /><br /></span><span style="color: #0000BB">$d</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">foo&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">;<br />echo&nbsp;</span><span style="color: #0000BB">$c</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">foo</span><span style="color: #007700">.</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /><br /></span><span style="color: #0000BB">$e&nbsp;</span><span style="color: #007700">=&nbsp;new&nbsp;</span><span style="color: #0000BB">A</span><span style="color: #007700">;<br /><br />function&nbsp;</span><span style="color: #0000BB">foo</span><span style="color: #007700">(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #FF8000">//&nbsp;($obj)&nbsp;=&nbsp;($e)&nbsp;=&nbsp;&lt;id&gt;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">foo&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">foo</span><span style="color: #007700">(</span><span style="color: #0000BB">$e</span><span style="color: #007700">);<br />echo&nbsp;</span><span style="color: #0000BB">$e</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">foo</span><span style="color: #007700">.</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
   </div>

   <div class="example-contents para"><p>The above example will output:</p></div>
   <div class="example-contents screen">
<div class="cdata"><pre>
2
2
2
</pre></div>
   </div>
  </div>
 </div><?php manual_footer(); ?>
 
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