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</div><hr /><div id="language.oop5.references" class="sect1">
<h2 class="title">Objects and references</h2>
<p class="para">
One of the key-points of PHP 5 OOP that is often mentioned is that
"objects are passed by references by default". 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 PHP 5, an object variable doesn'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" id="example-232">
<p><strong>Example #1 References and Objects</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">class </span><span style="color: #0000BB">A </span><span style="color: #007700">{<br /> public </span><span style="color: #0000BB">$foo </span><span style="color: #007700">= </span><span style="color: #0000BB">1</span><span style="color: #007700">;<br />} <br /><br /></span><span style="color: #0000BB">$a </span><span style="color: #007700">= new </span><span style="color: #0000BB">A</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$b </span><span style="color: #007700">= </span><span style="color: #0000BB">$a</span><span style="color: #007700">; </span><span style="color: #FF8000">// $a and $b are copies of the same identifier<br /> // ($a) = ($b) = <id><br /></span><span style="color: #0000BB">$b</span><span style="color: #007700">-></span><span style="color: #0000BB">foo </span><span style="color: #007700">= </span><span style="color: #0000BB">2</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">$a</span><span style="color: #007700">-></span><span style="color: #0000BB">foo</span><span style="color: #007700">.</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /><br /></span><span style="color: #0000BB">$c </span><span style="color: #007700">= new </span><span style="color: #0000BB">A</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">$d </span><span style="color: #007700">= &</span><span style="color: #0000BB">$c</span><span style="color: #007700">; </span><span style="color: #FF8000">// $c and $d are references<br /> // ($c,$d) = <id><br /><br /></span><span style="color: #0000BB">$d</span><span style="color: #007700">-></span><span style="color: #0000BB">foo </span><span style="color: #007700">= </span><span style="color: #0000BB">2</span><span style="color: #007700">;<br />echo </span><span style="color: #0000BB">$c</span><span style="color: #007700">-></span><span style="color: #0000BB">foo</span><span style="color: #007700">.</span><span style="color: #DD0000">"\n"</span><span style="color: #007700">;<br /><br /><br /></span><span style="color: #0000BB">$e </span><span style="color: #007700">= new </span><span style="color: #0000BB">A</span><span style="color: #007700">;<br /><br />function </span><span style="color: #0000BB">foo</span><span style="color: #007700">(</span><span style="color: #0000BB">$obj</span><span style="color: #007700">) {<br /> </span><span style="color: #FF8000">// ($obj) = ($e) = <id><br /> </span><span style="color: #0000BB">$obj</span><span style="color: #007700">-></span><span style="color: #0000BB">foo </span><span style="color: #007700">= </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">$e</span><span style="color: #007700">);<br />echo </span><span style="color: #0000BB">$e</span><span style="color: #007700">-></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">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
2
2
2
</pre></div>
</div>
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