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<refentry xml:id="function.strtotime" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
 <refnamediv>
  <refname>strtotime</refname>
  <refpurpose>Parse about any English textual datetime description into a Unix timestamp</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type class="union"><type>int</type><type>false</type></type><methodname>strtotime</methodname>
   <methodparam><type>string</type><parameter>datetime</parameter></methodparam>
   <methodparam choice="opt"><type class="union"><type>int</type><type>null</type></type><parameter>baseTimestamp</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <simpara>
   The function expects to be given a string containing an English date format
   and will try to parse that format into a Unix timestamp (the number of
   seconds since January 1 1970 00:00:00 UTC), relative to the timestamp given
   in <parameter>baseTimestamp</parameter>, or the current time if
   <parameter>baseTimestamp</parameter> is not supplied.  The date string parsing
   is defined in <link linkend="datetime.formats">Date and Time Formats</link>, and
   has several subtle considerations.  Reviewing the full details there is strongly
   recommended.
  </simpara>
  <warning>
   <para>
    The Unix timestamp that this function returns does not contain information
    about time zones. In order to do calculations with date/time information,
    you should use the more capable <classname>DateTimeImmutable</classname>.
   </para>
  </warning>
  <para>
   Each parameter of this function uses the default time zone unless a
   time zone is specified in that parameter.  Be careful not to use
   different time zones in each parameter unless that is intended.
   See <function>date_default_timezone_get</function> on the various
   ways to define the default time zone.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>datetime</parameter></term>
     <listitem>
      <para>&date.formats.parameter;</para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>baseTimestamp</parameter></term>
     <listitem>
      <para>
       The timestamp which is used as a base for the calculation of relative
       dates.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns a timestamp on success, &false; otherwise.
  </para>
 </refsect1>

 <refsect1 role="errors">
  &reftitle.errors;
   
   &date.timezone.errors.description;
 
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>8.0.0</entry>
       <entry>
        <parameter>baseTimestamp</parameter> is nullable now.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>A <function>strtotime</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
echo strtotime("now"), "\n";
echo strtotime("10 September 2000"), "\n";
echo strtotime("+1 day"), "\n";
echo strtotime("+1 week"), "\n";
echo strtotime("+1 week 2 days 4 hours 2 seconds"), "\n";
echo strtotime("next Thursday"), "\n";
echo strtotime("last Monday"), "\n";
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title>Checking for failure</title>
    <programlisting role="php">
<![CDATA[
<?php
$str = 'Not Good';

if (($timestamp = strtotime($str)) === false) {
    echo "The string ($str) is bogus";
} else {
    echo "$str == " . date('l dS \o\f F Y h:i:s A', $timestamp);
}
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  <note>
   <para>
    "Relative" date in this case also means that if a particular component
    of the date/time stamp is not provided, it will be taken verbatim from
    the <parameter>baseTimestamp</parameter>.  That is, <code>strtotime('February')</code>,
    if run on the 31st of May 2022, will be interpreted as <literal>31 February 2022</literal>,
    which will overflow into a timestamp on <literal>3 March</literal>.
    (In a leap year, it would be <literal>2 March</literal>.)  Using
    <code>strtotime('1 February')</code> or <code>strtotime('first day of February')</code>
    would avoid that problem.
   </para>
  </note>
  <note>
   <para>
    If the number of the year is specified in a two digit format, the values
    between 00-69 are mapped to 2000-2069 and 70-99 to 1970-1999. See the notes
    below for possible differences on 32bit systems (possible dates might end on 
    2038-01-19 03:14:07).
   </para>
  </note>
  <note>
   <para>
    The valid range of a timestamp is typically from Fri, 13 Dec
    1901 20:45:54 UTC to Tue, 19 Jan 2038 03:14:07 UTC. (These are
    the dates that correspond to the minimum and maximum values for
    a 32-bit signed integer.)
   </para>
   <para>
    For 64-bit versions of PHP, the valid range of a timestamp is effectively
    infinite, as 64 bits can represent approximately 293 billion years in either
    direction.
   </para>
  </note>
  <note>
   <para>
    Using this function for mathematical operations is not advisable.
    It is better to use <methodname>DateTime::add</methodname> and
    <methodname>DateTime::sub</methodname>.
   </para>
  </note>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><classname>DateTimeImmutable</classname></member>
    <member><methodname>DateTimeImmutable::createFromFormat</methodname></member>
    <member><link linkend="datetime.formats">Date and Time Formats</link></member>
    <member><function>checkdate</function></member>
    <member><function>strptime</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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