php-doc-en/reference/datetime/functions/strtotime.xml
Christoph Michael Becker bbed905d26 clarified behavior of nn-nn-nn parsing (fixes #61314)
git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@337698 c90b9560-bf6c-de11-be94-00142212c4b1
2015-09-01 23:52:22 +00:00

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<?xml version="1.0" encoding="utf-8"?>
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<!-- 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>int</type><methodname>strtotime</methodname>
<methodparam><type>string</type><parameter>time</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>now</parameter><initializer>time()</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>now</parameter>, or the current time if
<parameter>now</parameter> is not supplied.
</simpara>
<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>time</parameter></term>
<listitem>
<para>&date.formats.parameter;</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>now</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. Previous to PHP 5.1.0,
this function would return <literal>-1</literal> on failure.
</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>5.3.0</entry>
<entry>
Prior to PHP 5.3.0, relative time formats supplied to the
<parameter>time</parameter> argument of <function>strtotime</function>
such as <literal>this week</literal>, <literal>previous week</literal>,
<literal>last week</literal>, and <literal>next week</literal> were
interpreted to mean a 7 day period relative to the current date/time, rather
than a week period of <literal>Monday</literal> through <literal>Sunday</literal>.
</entry>
</row>
<row>
<entry>5.3.0</entry>
<entry>
Prior to PHP 5.3.0, <literal>24:00</literal> was not a valid format and
<function>strtotime</function> returned &false;.
</entry>
</row>
<row>
<entry>5.2.7</entry>
<entry>
In PHP 5 prior to 5.2.7, requesting a given occurrence of a
given weekday in a month where that weekday was the first day
of the month would incorrectly add one week to the returned
timestamp. This has been corrected in 5.2.7 and later
versions.
</entry>
</row>
<row>
<entry>5.1.0</entry>
<entry>
Now returns &false; on failure, instead
of <literal>-1</literal>.
</entry>
</row>
&date.timezone.errors.changelog;
<row>
<entry>5.0.2</entry>
<entry>
In PHP 5 up to 5.0.2, <literal>"now"</literal> and other
relative times are wrongly computed from today's
midnight. This differs from other versions where it is
correctly computed from current time.
</entry>
</row>
<row>
<entry>5.0.0</entry>
<entry>
Microseconds began to be allowed, but they are ignored.
</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
$str = 'Not Good';
// previous to PHP 5.1.0 you would compare with -1, instead of false
if (($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>
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>
Prior to PHP 5.1.0, not all platforms support negative timestamps, therefore
your date range may be limited to no earlier than the Unix epoch. This
means that e.g. dates prior to Jan 1, 1970 will not work on Windows,
some Linux distributions, and a few other operating systems.
</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>
Dates in the <literal>m/d/y</literal> or <literal>d-m-y</literal> formats
are disambiguated by looking at the separator between the various
components: if the separator is a slash (<literal>/</literal>), then the
American <literal>m/d/y</literal> is assumed; whereas if the separator is a
dash (<literal>-</literal>) or a dot (<literal>.</literal>), then the
European <literal>d-m-y</literal> format is assumed.
If, however, the year is given in a two digit format and the separator is a
dash (<literal>-</literal>, the date string is parsed as
<literal>y-m-d</literal>.
</para>
<para>
To avoid potential ambiguity, it's best to use ISO 8601
(<literal>YYYY-MM-DD</literal>) dates or
<methodname>DateTime::createFromFormat</methodname> when possible.
</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> in PHP 5.3 and later, or
<methodname>DateTime::modify</methodname> in PHP 5.2.
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><link linkend="datetime.formats">Date and Time Formats</link></member>
<member><methodname>DateTime::createFromFormat</methodname></member>
<member><function>checkdate</function></member>
<member><function>strptime</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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