<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <title>Defines a named constant</title> </head> <body><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.constant.html">constant</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.defined.html">defined</a></div> <div class="up"><a href="ref.misc.html">Misc. Functions</a></div> <div class="home"><a href="index.html">PHP Manual</a></div> </div><hr /><div id="function.define" class="refentry"> <div class="refnamediv"> <h1 class="refname">define</h1> <p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">define</span> — <span class="dc-title">Defines a named constant</span></p> </div> <div class="refsect1 description" id="refsect1-function.define-description"> <h3 class="title">Description</h3> <div class="methodsynopsis dc-description"> <span class="type">bool</span> <span class="methodname"><strong>define</strong></span> ( <span class="methodparam"><span class="type">string</span> <code class="parameter">$name</code></span> , <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$value</code></span> [, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$case_insensitive</code><span class="initializer"> = <strong><code>FALSE</code></strong></span></span> ] )</div> <p class="para rdfs-comment"> Defines a named constant at runtime. </p> </div> <div class="refsect1 parameters" id="refsect1-function.define-parameters"> <h3 class="title">Parameters</h3> <p class="para"> <dl> <dt> <code class="parameter">name</code></dt> <dd> <p class="para"> The name of the constant. </p> </dd> <dt> <code class="parameter">value</code></dt> <dd> <p class="para"> The value of the constant. In PHP 5, <code class="parameter">value</code> must be a <span class="type"><span class="type scalar">scalar</span></span> value (<span class="type"><a href="language.types.integer.html" class="type integer">integer</a></span>, <span class="type"><a href="language.types.float.html" class="type float">float</a></span>, <span class="type"><a href="language.types.string.html" class="type string">string</a></span>, <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span>, or <strong><code>NULL</code></strong>). In PHP 7, <span class="type"><a href="language.types.array.html" class="type array">array</a></span> values are also accepted. </p> <div class="warning"><strong class="warning">Warning</strong> <p class="para"> While it is possible to define <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> constants, it is not recommended and may cause unpredictable behavior. </p> </div> </dd> <dt> <code class="parameter">case_insensitive</code></dt> <dd> <p class="para"> If set to <strong><code>TRUE</code></strong>, the constant will be defined case-insensitive. The default behavior is case-sensitive; i.e. <em>CONSTANT</em> and <em>Constant</em> represent different values. </p> <blockquote class="note"><p><strong class="note">Note</strong>: <p class="para"> Case-insensitive constants are stored as lower-case. </p> </p></blockquote> </dd> </dl> </p> </div> <div class="refsect1 returnvalues" id="refsect1-function.define-returnvalues"> <h3 class="title">Return Values</h3> <p class="para"> Returns <strong><code>TRUE</code></strong> on success or <strong><code>FALSE</code></strong> on failure. </p> </div> <div class="refsect1 changelog" id="refsect1-function.define-changelog"> <h3 class="title">Changelog</h3> <p class="para"> <table class="doctable informaltable"> <thead> <tr> <th>Version</th> <th>Description</th> </tr> </thead> <tbody class="tbody"> <tr> <td>7.3.0</td> <td> <code class="parameter">case_insensitive</code> has been deprecated and will be removed in version 8.0.0. </td> </tr> <tr> <td>7.0.0</td> <td> <span class="type"><a href="language.types.array.html" class="type array">array</a></span> values are allowed. </td> </tr> </tbody> </table> </p> </div> <div class="refsect1 examples" id="refsect1-function.define-examples"> <h3 class="title">Examples</h3> <p class="para"> <div class="example" id="example-4661"> <p><strong>Example #1 Defining Constants</strong></p> <div class="example-contents"> <div class="phpcode"><code><span style="color: #000000"> <span style="color: #0000BB"><?php<br />define</span><span style="color: #007700">(</span><span style="color: #DD0000">"CONSTANT"</span><span style="color: #007700">, </span><span style="color: #DD0000">"Hello world."</span><span style="color: #007700">);<br />echo </span><span style="color: #0000BB">CONSTANT</span><span style="color: #007700">; </span><span style="color: #FF8000">// outputs "Hello world."<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">Constant</span><span style="color: #007700">; </span><span style="color: #FF8000">// outputs "Constant" and issues a notice.<br /><br /></span><span style="color: #0000BB">define</span><span style="color: #007700">(</span><span style="color: #DD0000">"GREETING"</span><span style="color: #007700">, </span><span style="color: #DD0000">"Hello you."</span><span style="color: #007700">, </span><span style="color: #0000BB">true</span><span style="color: #007700">);<br />echo </span><span style="color: #0000BB">GREETING</span><span style="color: #007700">; </span><span style="color: #FF8000">// outputs "Hello you."<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">Greeting</span><span style="color: #007700">; </span><span style="color: #FF8000">// outputs "Hello you."<br /><br />// Works as of PHP 7<br /></span><span style="color: #0000BB">define</span><span style="color: #007700">(</span><span style="color: #DD0000">'ANIMALS'</span><span style="color: #007700">, array(<br /> </span><span style="color: #DD0000">'dog'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'cat'</span><span style="color: #007700">,<br /> </span><span style="color: #DD0000">'bird'<br /></span><span style="color: #007700">));<br />echo </span><span style="color: #0000BB">ANIMALS</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">]; </span><span style="color: #FF8000">// outputs "cat"<br /><br /></span><span style="color: #0000BB">?></span> </span> </code></div> </div> </div> </p> </div> <div class="refsect1 seealso" id="refsect1-function.define-seealso"> <h3 class="title">See Also</h3> <p class="para"> <ul class="simplelist"> <li class="member"><span class="function"><a href="function.defined.html" class="function" rel="rdfs-seeAlso">defined()</a> - Checks whether a given named constant exists</span></li> <li class="member"><span class="function"><a href="function.constant.html" class="function" rel="rdfs-seeAlso">constant()</a> - Returns the value of a constant</span></li> <li class="member">The section on <a href="language.constants.html" class="link">Constants</a></li> </ul> </p> </div> </div><hr /><div class="manualnavbar" style="text-align: center;"> <div class="prev" style="text-align: left; float: left;"><a href="function.constant.html">constant</a></div> <div class="next" style="text-align: right; float: right;"><a href="function.defined.html">defined</a></div> <div class="up"><a href="ref.misc.html">Misc. 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