Source of: /manual/en/function.is-null.php
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<div id="function.is-null" class="refentry">
<div class="refnamediv">
<h1 class="refname">is_null</h1>
<p class="verinfo">(PHP 4 >= 4.0.4, PHP 5)</p><p class="refpurpose"><span class="refname">is_null</span> — <span class="dc-title">
Finds whether a variable is <b><tt class="constant">NULL</tt></b>
</span></p>
</div>
<a name="function.is-null.description"></a><div class="refsect1 description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">bool</span> <span class="methodname"><b>is_null</b></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.php#language.types.mixed" class="type mixed">mixed</a></span> <tt class="parameter">$var</tt></span>
)</div>
<p class="para rdfs-comment">
Finds whether the given variable is <b><tt class="constant">NULL</tt></b>.
</p>
</div>
<a name="function.is-null.parameters"></a><div class="refsect1 parameters">
<h3 class="title">Parameters</h3>
<p class="para">
</p><dl>
<dt class="varlistentry">
<span class="term"><i><tt class="parameter">var</tt></i>
</span>
</dt><dd class="listitem">
<p class="para">
The variable being evaluated.
</p>
</dd>
</dl>
<p>
</p>
</div>
<a name="function.is-null.returnvalues"></a><div class="refsect1 returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns <b><tt class="constant">TRUE</tt></b> if <i><tt class="parameter">var</tt></i>
is <a href="language.types.null.php" class="type null">null</a>, <b><tt class="constant">FALSE</tt></b>
otherwise.
</p>
</div>
<a name="function.is-null.examples"></a><div class="refsect1 examples">
<h3 class="title">Examples</h3>
<p class="para">
</p><div class="example">
<p><b>Example #1 <b>is_null()</b> example</b></p>
<div class="example-contents programlisting">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />error_reporting</span><span style="color: #007700">(</span><span style="color: #0000BB">E_ALL</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$foo </span><span style="color: #007700">= </span><span style="color: #0000BB">NULL</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">is_null</span><span style="color: #007700">(</span><span style="color: #0000BB">$inexistent</span><span style="color: #007700">), </span><span style="color: #0000BB">is_null</span><span style="color: #007700">(</span><span style="color: #0000BB">$foo</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents screen">
<div class="cdata"><pre>
Notice: Undefined variable: inexistent in ...
bool(true)
bool(true)
</pre></div>
</div>
</div><p>
</p>
</div>
<a name="function.is-null.seealso"></a><div class="refsect1 seealso">
<h3 class="title">See Also</h3>
<p class="para">
</p><ul class="simplelist">
<li class="member">The <a href="language.types.null.php#language.types.null.syntax" class="link"><b><tt class="constant">NULL</tt></b></a> type</li>
<li class="member"><a href="function.isset.php" class="function" rel="rdfs-seeAlso">isset()</a> - Determine if a variable is set and is not NULL</li>
<li class="member"><a href="function.is-bool.php" class="function" rel="rdfs-seeAlso">is_bool()</a> - Finds out whether a variable is a boolean</li>
<li class="member"><a href="function.is-numeric.php" class="function" rel="rdfs-seeAlso">is_numeric()</a> - Finds whether a variable is a number or a numeric string</li>
<li class="member"><a href="function.is-float.php" class="function" rel="rdfs-seeAlso">is_float()</a> - Finds whether the type of a variable is float</li>
<li class="member"><a href="function.is-int.php" class="function" rel="rdfs-seeAlso">is_int()</a> - Find whether the type of a variable is integer</li>
<li class="member"><a href="function.is-string.php" class="function" rel="rdfs-seeAlso">is_string()</a> - Find whether the type of a variable is string</li>
<li class="member"><a href="function.is-object.php" class="function" rel="rdfs-seeAlso">is_object()</a> - Finds whether a variable is an object</li>
<li class="member"><a href="function.is-array.php" class="function" rel="rdfs-seeAlso">is_array()</a> - Finds whether a variable is an array</li>
</ul><p>
</p>
</div>
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