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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- splitted from ./en/functions/datetime.xml, last change in rev 1.8 -->
<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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