<HTML ><HEAD ><TITLE >defined</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE="PHP Manual" HREF="index.html"><LINK REL="UP" TITLE="Miscellaneous functions" HREF="ref.misc.html"><LINK REL="PREVIOUS" TITLE="define" HREF="function.define.html"><LINK REL="NEXT" TITLE="die" HREF="function.die.html"><META HTTP-EQUIV="Content-type" CONTENT="text/html; charset=ISO-8859-1"></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 Manual</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="function.define.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="function.die.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="function.defined" ></A >defined</H1 ><DIV CLASS="refnamediv" ><A NAME="AEN55420" ></A ><P > (PHP 3, PHP 4 )</P >defined -- Checks whether a given named constant exists </DIV ><DIV CLASS="refsect1" ><A NAME="AEN55423" ></A ><H2 >Description</H2 >bool <B CLASS="methodname" >defined</B > ( string name)<BR ></BR ><P > Returns <TT CLASS="constant" ><B >TRUE</B ></TT > if the named constant given by <TT CLASS="parameter" ><I >name</I ></TT > has been defined, <TT CLASS="constant" ><B >FALSE</B ></TT > otherwise. <TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" CLASS="EXAMPLE" ><TR ><TD ><DIV CLASS="example" ><A NAME="AEN55435" ></A ><P ><B >Example 1. Checking Constants</B ></P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" CELLPADDING="5" ><TR ><TD ><PRE CLASS="php" ><?php if (defined("CONSTANT")){ // Note that it should be quoted echo CONSTANT; // } ?></PRE ></TD ></TR ></TABLE ></DIV ></TD ></TR ></TABLE > </P ><P > See also <A HREF="function.define.html" ><B CLASS="function" >define()</B ></A >, <A HREF="function.constant.html" ><B CLASS="function" >constant()</B ></A >, <A HREF="function.get-defined-constants.html" ><B CLASS="function" >get_defined_constants()</B ></A > and the section on <A HREF="language.constants.html" >Constants</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.define.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="function.die.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >define</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ref.misc.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >die</TD ></TR ></TABLE ></DIV ></BODY ></HTML >