<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >is_a</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="Classes/Objects 类/对象函数" HREF="ref.classobj.html"><LINK REL="PREVIOUS" TITLE="interface_exists" HREF="function.interface-exists.html"><LINK REL="NEXT" TITLE="is_subclass_of" HREF="function.is-subclass-of.html"><META HTTP-EQUIV="Content-type" CONTENT="text/html; charset=UTF-8"></HEAD ><BODY CLASS="refentry" 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="function.interface-exists.html" ACCESSKEY="P" >上一页</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="function.is-subclass-of.html" ACCESSKEY="N" >下一页</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="function.is-a" ></A >is_a</H1 ><DIV CLASS="refnamediv" ><A NAME="AEN17077" ></A ><P > (PHP 4 >= 4.2.0, PHP 5)</P >is_a -- 如果对象属于该类或该类是此对象的父类则返回 <TT CLASS="constant" ><B >TRUE</B ></TT ></DIV ><DIV CLASS="refsect1" ><A NAME="AEN17081" ></A ><H2 >说明</H2 >bool <B CLASS="methodname" >is_a</B > ( object object, string class_name )<BR ></BR ><P > 如果对象是该类或该类是此对象的父类则返回 <TT CLASS="constant" ><B >TRUE</B ></TT >,否则返回 <TT CLASS="constant" ><B >FALSE</B ></TT >。 </P ><P > <TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" CLASS="EXAMPLE" ><TR ><TD ><DIV CLASS="example" ><A NAME="AEN17096" ></A ><P ><B >例 1. <B CLASS="function" >is_a()</B > 例子</B ></P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" CELLPADDING="5" ><TR ><TD ><code><font color="#000000"> <font color="#0000BB"><?php<br /></font><font color="#FF8000">// define a class<br /></font><font color="#007700">class </font><font color="#0000BB">WidgetFactory<br /></font><font color="#007700">{<br /> var </font><font color="#0000BB">$oink </font><font color="#007700">= </font><font color="#DD0000">'moo'</font><font color="#007700">;<br />}<br /><br /></font><font color="#FF8000">// create a new object<br /></font><font color="#0000BB">$WF </font><font color="#007700">= new </font><font color="#0000BB">WidgetFactory</font><font color="#007700">();<br /><br />if (</font><font color="#0000BB">is_a</font><font color="#007700">(</font><font color="#0000BB">$WF</font><font color="#007700">, </font><font color="#DD0000">'WidgetFactory'</font><font color="#007700">)) {<br /> echo </font><font color="#DD0000">"yes, \$WF is still a WidgetFactory\n"</font><font color="#007700">;<br />}<br /></font><font color="#0000BB">?></font> </font> </code></TD ></TR ></TABLE ></DIV ></TD ></TR ></TABLE > </P ><P > <B CLASS="function" >is_a()</B > 函数已废弃,自 PHP 5 起请使用 <A HREF="language.operators.type.html" >instanceof</A > 类型运算符。上例在 PHP 5 中会是这样: </P ><P > <TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" CLASS="EXAMPLE" ><TR ><TD ><DIV CLASS="example" ><A NAME="AEN17104" ></A ><P ><B >例 2. 在 PHP 5 中使用 <SPAN CLASS="emphasis" ><I CLASS="emphasis" >instanceof</I ></SPAN > 运算符</B ></P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" CELLPADDING="5" ><TR ><TD ><code><font color="#000000"> <font color="#0000BB"><?php<br /></font><font color="#007700">if (</font><font color="#0000BB">$WF instanceof WidgetFactory</font><font color="#007700">) {<br /> echo </font><font color="#DD0000">'Yes, $WF is a WidgetFactory'</font><font color="#007700">;<br />}<br /></font><font color="#0000BB">?></font> </font> </code></TD ></TR ></TABLE ></DIV ></TD ></TR ></TABLE > </P ><P > 参见 <A HREF="function.get-class.html" ><B CLASS="function" >get_class()</B ></A >,<A HREF="function.get-parent-class.html" ><B CLASS="function" >get_parent_class()</B ></A > 和 <A HREF="function.is-subclass-of.html" ><B CLASS="function" >is_subclass_of()</B ></A >。 </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="function.interface-exists.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="function.is-subclass-of.html" ACCESSKEY="N" >下一页</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >interface_exists</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ref.classobj.html" ACCESSKEY="U" >上一级</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >is_subclass_of</TD ></TR ></TABLE ></DIV ></BODY ></HTML >