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<refentry xml:id="function.filter-var" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>filter_var</refname>
  <refpurpose>Filters a variable with a specified filter</refpurpose>
 </refnamediv>

 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>mixed</type><methodname>filter_var</methodname>
   <methodparam><type>mixed</type><parameter>value</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>filter</parameter><initializer><constant>FILTER_DEFAULT</constant></initializer></methodparam>
   <methodparam choice="opt"><type class="union"><type>array</type><type>int</type></type><parameter>options</parameter><initializer>0</initializer></methodparam>
  </methodsynopsis>
  <simpara>
   Filter a variable using a
   <constant>FILTER_VALIDATE_<replaceable>*</replaceable></constant>
   validation filters, a
   <constant>FILTER_SANITIZE_<replaceable>*</replaceable></constant>
   sanitization filters, or a custom filter.
  </simpara>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <variablelist>
   <varlistentry>
    <term><parameter>value</parameter></term>
    <listitem>
     <simpara>
      Value to filter.
     </simpara>
     <warning>
      <simpara>
       Scalar values are
       <link linkend="language.types.string.casting">converted to string</link>
       internally before they are filtered.
      </simpara>
     </warning>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term><parameter>filter</parameter></term>
    <listitem>
     <simpara>
      The filter to apply.
      Can be a validation filter by using one of the
      <constant>FILTER_VALIDATE_<replaceable>*</replaceable></constant>
      constants, a sanitization filter by using one of the
      <constant>FILTER_SANITIZE_<replaceable>*</replaceable></constant>
      or <constant>FILTER_UNSAFE_RAW</constant>, or a custom filter by using
      <constant>FILTER_CALLBACK</constant>.
     </simpara>
     <note>
      <simpara>
       The default is <constant>FILTER_DEFAULT</constant>,
       which is an alias of <constant>FILTER_UNSAFE_RAW</constant>.
       This will result in no filtering taking place by default.
      </simpara>
     </note>
    </listitem>
   </varlistentry>
   <varlistentry>
    <term><parameter>options</parameter></term>
    <listitem>
     <simpara>
      Either an associative <type>array</type> of options,
      or a bitmask of filter flag constants
      <constant>FILTER_FLAG_<replaceable>*</replaceable></constant>.
     </simpara>
     <simpara>
      If the <parameter>filter</parameter> accepts options,
      flags can be provided by using the <literal>"flags"</literal> field of array.
     </simpara>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <simpara>
   On success returns the filtered data.
   On failure &false; is returned,
   unless the <constant>FILTER_NULL_ON_FAILURE</constant> flag is used,
   in which case &null; is returned.
  </simpara>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <example>
   <title>A <function>filter_var</function> example</title>
   <programlisting role="php">
<![CDATA[
<?php
var_dump(filter_var('bob@example.com', FILTER_VALIDATE_EMAIL));
var_dump(filter_var('https://example.com', FILTER_VALIDATE_URL, FILTER_FLAG_PATH_REQUIRED));
?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
string(15) "bob@example.com"
bool(false)
]]>
   </screen>
  </example>

  <example>
   <title>Example validating entries of an array</title>
   <programlisting role="php">
<![CDATA[
<?php
$emails = [
    "bob@example.com",
    "test@example.local",
    "invalidemail"
];

var_dump(filter_var($emails, FILTER_VALIDATE_EMAIL, FILTER_REQUIRE_ARRAY));
?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
array(3) {
  [0]=>
  string(15) "bob@example.com"
  [1]=>
  string(18) "test@example.local"
  [2]=>
  bool(false)
}
]]>
   </screen>
  </example>

  <example>
   <title>Example of passing an array for <parameter>options</parameter></title>
   <programlisting role="php">
<![CDATA[
<?php

$options = [
    'options' => [
        'min_range' => 10,
    ],
    'flags' => FILTER_FLAG_ALLOW_OCTAL,
];

var_dump(filter_var('0755', FILTER_VALIDATE_INT, $options));
var_dump(filter_var('011', FILTER_VALIDATE_INT, $options));

?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
int(493)
bool(false)
]]>
   </screen>
  </example>

  <example>
   <title>Providing flags either directly or via an <type>array</type></title>
   <programlisting role="php">
<![CDATA[
<?php

$str = 'string';

var_dump(filter_var($str, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE));
var_dump(filter_var($str, FILTER_VALIDATE_BOOLEAN, ['flags' => FILTER_NULL_ON_FAILURE]));

?>
]]>
   </programlisting>
   &example.outputs;
   <screen>
<![CDATA[
NULL
NULL
]]>
   </screen>
  </example>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <simplelist>
   <member><function>filter_var_array</function></member>
   <member><function>filter_input</function></member>
   <member><function>filter_input_array</function></member>
   <member>
    Validation filters
    <constant>FILTER_VALIDATE_<replaceable>*</replaceable></constant>
   </member>
   <member>
    Sanitization filters
    <constant>FILTER_SANITIZE_<replaceable>*</replaceable></constant>
   </member>
  </simplelist>
 </refsect1>

</refentry>
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