<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >逻辑运算符</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="运算符" HREF="language.operators.html"><LINK REL="PREVIOUS" TITLE="递增/递减运算符" HREF="language.operators.increment.html"><LINK REL="NEXT" TITLE="字符串运算符" HREF="language.operators.string.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.operators.increment.html" ACCESSKEY="P" >上一页</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >章 15. 运算符</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="language.operators.string.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.operators.logical" >逻辑运算符</A ></H1 ><DIV CLASS="table" ><A NAME="AEN4500" ></A ><P ><B >表 15-7. 逻辑运算符</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><THEAD ><TR ><TH >例子</TH ><TH >名称</TH ><TH >结果</TH ></TR ></THEAD ><TBODY ><TR ><TD >$a and $b</TD ><TD >And(逻辑与)</TD ><TD ><TT CLASS="constant" ><B >TRUE</B ></TT >,如果 $a 与 $b 都为 <TT CLASS="constant" ><B >TRUE</B ></TT >。</TD ></TR ><TR ><TD >$a or $b</TD ><TD >Or(逻辑或)</TD ><TD ><TT CLASS="constant" ><B >TRUE</B ></TT >,如果 $a 或 $b 任一为 <TT CLASS="constant" ><B >TRUE</B ></TT >。</TD ></TR ><TR ><TD >$a xor $b</TD ><TD >Xor(逻辑异或)</TD ><TD ><TT CLASS="constant" ><B >TRUE</B ></TT >,如果 $a 或 $b 任一为 <TT CLASS="constant" ><B >TRUE</B ></TT >,但不同时是。</TD ></TR ><TR ><TD >! $a</TD ><TD >Not(逻辑非)</TD ><TD ><TT CLASS="constant" ><B >TRUE</B ></TT >,如果 $a 不为 <TT CLASS="constant" ><B >TRUE</B ></TT >。</TD ></TR ><TR ><TD >$a && $b</TD ><TD >And(逻辑与)</TD ><TD ><TT CLASS="constant" ><B >TRUE</B ></TT >,如果 $a 与 $b 都为 <TT CLASS="constant" ><B >TRUE</B ></TT >。</TD ></TR ><TR ><TD >$a || $b</TD ><TD >Or(逻辑或)</TD ><TD ><TT CLASS="constant" ><B >TRUE</B ></TT >,如果 $a 或 $b 任一为 <TT CLASS="constant" ><B >TRUE</B ></TT >。</TD ></TR ></TBODY ></TABLE ></DIV ><P > “与”和“或”有两种不同形式运算符的原因是它们运算的优先级不同(见<A HREF="language.operators.html#language.operators.precedence" >运算符优先级</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="language.operators.increment.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.operators.string.html" ACCESSKEY="N" >下一页</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >递增/递减运算符</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="language.operators.html" ACCESSKEY="U" >上一级</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >字符串运算符</TD ></TR ></TABLE ></DIV ></BODY ></HTML >