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<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>
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