php-doc-en/reference/datetime/functions/strtotime.xml
Adam Harvey ef151ba6c1 Removed the reference to "US English" in the strtotime() description, since
that's not true for all delimiters, and added an explanatory note summarising
the Date and Time Formats grammar and how it pertains to m/d/y and d-m-y, along
with a recommendation to use ISO 8601 or DateTime::createFromFormat() where
possible.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@305220 c90b9560-bf6c-de11-be94-00142212c4b1
2010-11-09 10:53:51 +00:00

249 lines
7.2 KiB
XML

<?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>int</type><methodname>strtotime</methodname>
<methodparam><type>string</type><parameter>time</parameter></methodparam>
<methodparam choice="opt"><type>int</type><parameter>now</parameter></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>
This function will use the <envar>TZ</envar> environment variable (if
available) to calculate the timestamp. Since PHP 5.1.0 there are easier
ways to define the timezone that is used across all date/time functions.
That process is explained in the
<function>date_default_timezone_get</function> function page.
</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, <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>
<row>
<entry>4.4.0</entry>
<entry>
In PHP versions prior to 4.4.0, <literal>"next"</literal> is incorrectly
computed as +2. A typical solution to this is to use
<literal>"+1"</literal>.
</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.)
Additionally, 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. PHP 5.1.0 and
newer versions overcome this limitation though.
</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.
</para>
<para>
To avoid potential ambiguity, it's best to use ISO 8601
(<literal>YYYY-MM-DD</literal>) dates or
<function>DateTime::createFromFormat</function> when possible.
</para>
</note>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>DateTime::createFromFormat</function></member>
<member><function>strptime</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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