<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Comparing objects</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REL="HOME"
TITLE="PHP 手册"
HREF="index.html"><LINK
REL="UP"
TITLE="类与对象（PHP 5）"
HREF="language.oop5.html"><LINK
REL="PREVIOUS"
TITLE="Object cloning"
HREF="language.oop5.cloning.html"><LINK
REL="NEXT"
TITLE="Reflection"
HREF="language.oop5.reflection.html"><META
HTTP-EQUIV="Content-type"
CONTENT="text/html; charset=UTF-8"></HEAD
><BODY
CLASS="sect1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>PHP 手册</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="language.oop5.cloning.html"
ACCESSKEY="P"
>上一页</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>章 19. 类与对象（PHP 5）</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="language.oop5.reflection.html"
ACCESSKEY="N"
>下一页</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="sect1"
><H1
CLASS="sect1"
><A
NAME="language.oop5.object-comparison"
>Comparing objects</A
></H1
><P
> In PHP 5, object comparison is more complicated than in PHP 4 and more
in accordance to what one will expect from an Object Oriented Language
(not that PHP 5 is such a language).
</P
><P
> When using the comparison operator (<TT
CLASS="literal"
>==</TT
>),
object variables are compared in a simple manner, namely: Two object
instances are equal if they have the same attributes and values, and are
instances of the same class.
</P
><P
> On the other hand, when using the identity operator (<TT
CLASS="literal"
>===</TT
>),
object variables are identical if and only if they refer to the same
instance of the same class.
</P
><P
> An example will clarify these rules.
<TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN6099"
></A
><P
><B
>例 19-32. Example of object comparison in PHP 5</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><code><font color="#000000">
<font color="#0000BB"><?php<br /></font><font color="#007700">function </font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$bool</font><font color="#007700">)<br />{<br /> if (</font><font color="#0000BB">$bool </font><font color="#007700">=== </font><font color="#0000BB">false</font><font color="#007700">) {<br /> return </font><font color="#DD0000">'FALSE'</font><font color="#007700">;<br /> } else {<br /> return </font><font color="#DD0000">'TRUE'</font><font color="#007700">;<br /> }<br />}<br /><br />function </font><font color="#0000BB">compareObjects</font><font color="#007700">(&</font><font color="#0000BB">$o1</font><font color="#007700">, &</font><font color="#0000BB">$o2</font><font color="#007700">)<br />{<br /> echo </font><font color="#DD0000">'o1 == o2 : ' </font><font color="#007700">. </font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$o1 </font><font color="#007700">== </font><font color="#0000BB">$o2</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /> echo </font><font color="#DD0000">'o1 != o2 : ' </font><font color="#007700">. </font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$o1 </font><font color="#007700">!= </font><font color="#0000BB">$o2</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /> echo </font><font color="#DD0000">'o1 === o2 : ' </font><font color="#007700">. </font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$o1 </font><font color="#007700">=== </font><font color="#0000BB">$o2</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br /> echo </font><font color="#DD0000">'o1 !== o2 : ' </font><font color="#007700">. </font><font color="#0000BB">bool2str</font><font color="#007700">(</font><font color="#0000BB">$o1 </font><font color="#007700">!== </font><font color="#0000BB">$o2</font><font color="#007700">) . </font><font color="#DD0000">"\n"</font><font color="#007700">;<br />}<br /><br />class </font><font color="#0000BB">Flag<br /></font><font color="#007700">{<br /> </font><font color="#0000BB">public $flag</font><font color="#007700">;<br /><br /> function </font><font color="#0000BB">Flag</font><font color="#007700">(</font><font color="#0000BB">$flag </font><font color="#007700">= </font><font color="#0000BB">true</font><font color="#007700">) {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">flag </font><font color="#007700">= </font><font color="#0000BB">$flag</font><font color="#007700">;<br /> }<br />}<br /><br />class </font><font color="#0000BB">OtherFlag<br /></font><font color="#007700">{<br /> </font><font color="#0000BB">public $flag</font><font color="#007700">;<br /><br /> function </font><font color="#0000BB">OtherFlag</font><font color="#007700">(</font><font color="#0000BB">$flag </font><font color="#007700">= </font><font color="#0000BB">true</font><font color="#007700">) {<br /> </font><font color="#0000BB">$this</font><font color="#007700">-></font><font color="#0000BB">flag </font><font color="#007700">= </font><font color="#0000BB">$flag</font><font color="#007700">;<br /> }<br />}<br /><br /></font><font color="#0000BB">$o </font><font color="#007700">= new </font><font color="#0000BB">Flag</font><font color="#007700">();<br /></font><font color="#0000BB">$p </font><font color="#007700">= new </font><font color="#0000BB">Flag</font><font color="#007700">();<br /></font><font color="#0000BB">$q </font><font color="#007700">= </font><font color="#0000BB">$o</font><font color="#007700">;<br /></font><font color="#0000BB">$r </font><font color="#007700">= new </font><font color="#0000BB">OtherFlag</font><font color="#007700">();<br /><br />echo </font><font color="#DD0000">"Two instances of the same class\n"</font><font color="#007700">;<br /></font><font color="#0000BB">compareObjects</font><font color="#007700">(</font><font color="#0000BB">$o</font><font color="#007700">, </font><font color="#0000BB">$p</font><font color="#007700">);<br /><br />echo </font><font color="#DD0000">"\nTwo references to the same instance\n"</font><font color="#007700">;<br /></font><font color="#0000BB">compareObjects</font><font color="#007700">(</font><font color="#0000BB">$o</font><font color="#007700">, </font><font color="#0000BB">$q</font><font color="#007700">);<br /><br />echo </font><font color="#DD0000">"\nInstances of two different classes\n"</font><font color="#007700">;<br /></font><font color="#0000BB">compareObjects</font><font color="#007700">(</font><font color="#0000BB">$o</font><font color="#007700">, </font><font color="#0000BB">$r</font><font color="#007700">);<br /></font><font color="#0000BB">?></font>
</font>
</code></TD
></TR
></TABLE
><P
>上例将输出：</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="screen"
>Two instances of the same class
o1 == o2 : TRUE
o1 != o2 : FALSE
o1 === o2 : FALSE
o1 !== o2 : TRUE
Two references to the same instance
o1 == o2 : TRUE
o1 != o2 : FALSE
o1 === o2 : TRUE
o1 !== o2 : FALSE
Instances of two different classes
o1 == o2 : FALSE
o1 != o2 : TRUE
o1 === o2 : FALSE
o1 !== o2 : TRUE</PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
</P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="language.oop5.cloning.html"
ACCESSKEY="P"
>上一页</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>起始页</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="language.oop5.reflection.html"
ACCESSKEY="N"
>下一页</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Object cloning</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="language.oop5.html"
ACCESSKEY="U"
>上一级</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Reflection</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
