php-doc-en/reference/strings/functions/htmlentities.xml

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<refentry xml:id="function.htmlentities" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>htmlentities</refname>
  <refpurpose>Convert all applicable characters to HTML entities</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>htmlentities</methodname>
   <methodparam><type>string</type><parameter>string</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>flags</parameter><initializer><constant>ENT_QUOTES</constant> | <constant>ENT_SUBSTITUTE</constant> | <constant>ENT_HTML401</constant></initializer></methodparam>
   <methodparam choice="opt"><type class="union"><type>string</type><type>null</type></type><parameter>encoding</parameter><initializer>&null;</initializer></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>double_encode</parameter><initializer>&true;</initializer></methodparam>
  </methodsynopsis>
  <para>
   This function is identical to <function>htmlspecialchars</function> in all
   ways, except with <function>htmlentities</function>, all characters which
   have HTML character entity equivalents are translated into these entities.
  </para>
  <para>
   If you want to decode instead (the reverse) you can use
   <function>html_entity_decode</function>.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>string</parameter></term>
     <listitem>
      <para>
       The input string.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>flags</parameter></term>
     <listitem>
      <para>
       A bitmask of one or more of the following flags, which specify how to handle quotes,
       invalid code unit sequences and the used document type. The default is
       <literal>ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML401</literal>.
       <table>
        <title>Available <parameter>flags</parameter> constants</title>
        <tgroup cols="2">
         <thead>
          <row>
           <entry>Constant Name</entry>
           <entry>Description</entry>
          </row>
         </thead>
         <tbody>
          <row>
           <entry><constant>ENT_COMPAT</constant></entry>
           <entry>Will convert double-quotes and leave single-quotes alone.</entry>
          </row>
          <row>
           <entry><constant>ENT_QUOTES</constant></entry>
           <entry>Will convert both double and single quotes.</entry>
          </row>
          <row>
           <entry><constant>ENT_NOQUOTES</constant></entry>
           <entry>Will leave both double and single quotes unconverted.</entry>
          </row>
          <row>
           <entry><constant>ENT_IGNORE</constant></entry>
           <entry>
            Silently discard invalid code unit sequences instead of returning
            an empty string. Using this flag is discouraged as it
            <link xlink:href="&url.delete.nonchars;">may have security implications</link>.
           </entry>
          </row>
          <row>
           <entry><constant>ENT_SUBSTITUTE</constant></entry>
           <entry>
            Replace invalid code unit sequences with a Unicode Replacement Character
            U+FFFD (UTF-8) or &amp;#FFFD; (otherwise) instead of returning an empty string.
           </entry>
          </row>
          <row>
           <entry><constant>ENT_DISALLOWED</constant></entry>
           <entry>
            Replace invalid code points for the given document type with a
            Unicode Replacement Character U+FFFD (UTF-8) or &amp;#FFFD;
            (otherwise) instead of leaving them as is. This may be useful, for
            instance, to ensure the well-formedness of XML documents with
            embedded external content.
           </entry>
          </row>
          <row>
           <entry><constant>ENT_HTML401</constant></entry>
           <entry>
            Handle code as HTML 4.01.
           </entry>
          </row>
          <row>
           <entry><constant>ENT_XML1</constant></entry>
           <entry>
            Handle code as XML 1.
           </entry>
          </row>
          <row>
           <entry><constant>ENT_XHTML</constant></entry>
           <entry>
            Handle code as XHTML.
           </entry>
          </row>
          <row>
           <entry><constant>ENT_HTML5</constant></entry>
           <entry>
            Handle code as HTML 5.
           </entry>
          </row>
         </tbody>
        </tgroup>
       </table>
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>encoding</parameter></term>
     <listitem>
      &strings.parameter.encoding;
      &reference.strings.charsets;
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>double_encode</parameter></term>
     <listitem>
      <para>
       When <parameter>double_encode</parameter> is turned off PHP will not
       encode existing html entities. The default is to convert everything.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the encoded string.
  </para>
  <para>
   If the input <parameter>string</parameter> contains an invalid code unit
   sequence within the given <parameter>encoding</parameter> an empty string
   will be returned, unless either the <constant>ENT_IGNORE</constant> or
   <constant>ENT_SUBSTITUTE</constant> flags are set.
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.1.0</entry>
      <entry>
       <parameter>flags</parameter> changed from <constant>ENT_COMPAT</constant> to <constant>ENT_QUOTES</constant> | <constant>ENT_SUBSTITUTE</constant> | <constant>ENT_HTML401</constant>.
      </entry>
     </row>
     <row>
      <entry>8.0.0</entry>
      <entry>
       <parameter>encoding</parameter> is nullable now.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>A <function>htmlentities</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$str = "A 'quote' is <b>bold</b>";

// Outputs: A 'quote' is &lt;b&gt;bold&lt;/b&gt;
echo htmlentities($str);

// Outputs: A &#039;quote&#039; is &lt;b&gt;bold&lt;/b&gt;
echo htmlentities($str, ENT_QUOTES);
?>
]]>
    </programlisting>
   </example>
  </para>
  
  <para>
   <example>
    <title>Usage of <constant>ENT_IGNORE</constant></title>
    <programlisting role="php">
<![CDATA[
<?php
$str = "\x8F!!!";

// Outputs an empty string
echo htmlentities($str, ENT_QUOTES, "UTF-8");

// Outputs "!!!"
echo htmlentities($str, ENT_QUOTES | ENT_IGNORE, "UTF-8");
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>html_entity_decode</function></member>
    <member><function>get_html_translation_table</function></member>
    <member><function>htmlspecialchars</function></member>
    <member><function>nl2br</function></member>
    <member><function>urlencode</function></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>
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