PHP - 获取一年中的最后一周数字

Question

请告诉我如何获得一年中的最后几周？

Answer 1

function getIsoWeeksInYear($year) {
    $date = new DateTime;
    $date->setISODate($year, 53);
    return ($date->format("W") === "53" ? 53 : 52);
}

The o date format gives the ISO-8601 year number . We can use this, and the fact that "invalid" dates are automatically rolled around to make valid ones ( 2011-02-31 gives 2011-03-03 ), to determine if a given year has 53 weeks. If does not, then it must have 52.

See also, date format characters and DateTime::setISODate() manual pages.

Answer 2

In ISO-8601 specification, it says that December 28th is always in the last week of its year .
Based on that, we can simply create that date, and see in what week it is:

$dt = new DateTime('December 28th');
echo $dt->format('W'); # 52

$dt = new DateTime('December 28th, 2009');
echo $dt->format('W'); # 53

demo

^{... or if you are using date() and strtotime() functions: echo date('W', strtotime('December 28th')); # 52 echo date('W', strtotime('December 28th')); # 52}

Answer 3

Replace 2010 by the year you want and Europe/Berlin with your timezone:

<?php
    date_default_timezone_set('Europe/Berlin');
    echo gmdate("W", strtotime("31 December 2010"));
?>

You'll get one of the values 01 , 52 or 53 .

---

Just for fun ( Demo ):

<?php
    date_default_timezone_set('Europe/Berlin');
    echo "ISO-8601 week number of year, weeks starting on Monday, of 31 December:\n\n";
    for ($year = 1900; $year < 2100; $year++) {
        $date = strtotime("31 December $year");
        echo "$year => ", gmdate("W", $date), "\n";
    }
?>

Output:

ISO-8601 week number of year, weeks starting on Monday, of 31 December:

1900 => 01
1901 => 01
1902 => 01
1903 => 53
1904 => 52
1905 => 52
1906 => 52
1907 => 01
1908 => 53
1909 => 52
1910 => 52
1911 => 52
1912 => 01
1913 => 01
1914 => 53
1915 => 52
1916 => 52
1917 => 52
1918 => 01
1919 => 01
1920 => 53
1921 => 52
1922 => 52
1923 => 52
1924 => 01
1925 => 53
1926 => 52
1927 => 52
1928 => 52
1929 => 01
1930 => 01
1931 => 53
1932 => 52
1933 => 52
1934 => 52
1935 => 01
1936 => 53
1937 => 52
1938 => 52
1939 => 52
1940 => 01
1941 => 01
1942 => 53
1943 => 52
1944 => 52
1945 => 52
1946 => 01
1947 => 01
1948 => 53
1949 => 52
1950 => 52
1951 => 52
1952 => 01
1953 => 53
1954 => 52
1955 => 52
1956 => 52
1957 => 01
1958 => 01
1959 => 53
1960 => 52
1961 => 52
1962 => 52
1963 => 01
1964 => 53
1965 => 52
1966 => 52
1967 => 52
1968 => 01
1969 => 01
1970 => 53
1971 => 52
1972 => 52
1973 => 52
1974 => 01
1975 => 01
1976 => 53
1977 => 52
1978 => 52
1979 => 52
1980 => 01
1981 => 53
1982 => 52
1983 => 52
1984 => 52
1985 => 01
1986 => 01
1987 => 53
1988 => 52
1989 => 52
1990 => 52
1991 => 01
1992 => 53
1993 => 52
1994 => 52
1995 => 52
1996 => 01
1997 => 01
1998 => 53
1999 => 52
2000 => 52
2001 => 52
2002 => 01
2003 => 01
2004 => 53
2005 => 52
2006 => 52
2007 => 52
2008 => 01
2009 => 53
2010 => 52
2011 => 52
2012 => 52
2013 => 01
2014 => 01
2015 => 53
2016 => 52
2017 => 52
2018 => 52
2019 => 01
2020 => 53
2021 => 52
2022 => 52
2023 => 52
2024 => 01
2025 => 01
2026 => 53
2027 => 52
2028 => 52
2029 => 52
2030 => 01
2031 => 01
2032 => 53
2033 => 52
2034 => 52
2035 => 52
2036 => 01
2037 => 53
2038 => 01
2039 => 01
2040 => 01
2041 => 01
2042 => 01
2043 => 01
2044 => 01
2045 => 01
2046 => 01
2047 => 01
2048 => 01
2049 => 01
2050 => 01
2051 => 01
2052 => 01
2053 => 01
2054 => 01
2055 => 01
2056 => 01
2057 => 01
2058 => 01
2059 => 01
2060 => 01
2061 => 01
2062 => 01
2063 => 01
2064 => 01
2065 => 01
2066 => 01
2067 => 01
2068 => 01
2069 => 01
2070 => 01
2071 => 01
2072 => 01
2073 => 01
2074 => 01
2075 => 01
2076 => 01
2077 => 01
2078 => 01
2079 => 01
2080 => 01
2081 => 01
2082 => 01
2083 => 01
2084 => 01
2085 => 01
2086 => 01
2087 => 01
2088 => 01
2089 => 01
2090 => 01
2091 => 01
2092 => 01
2093 => 01
2094 => 01
2095 => 01
2096 => 01
2097 => 01
2098 => 01
2099 => 01

Answer 4

If you were asking how to get the number of weeks left in the year, this would do it:

<?php

$year = date('Y');

$week_count = date('W', strtotime($year . '-12-31'));

if ($week_count == '01')
{   
    $week_count = date('W', strtotime($year . '-12-24'));
}

echo ($week_count - date('W'));
echo ' weeks left in ' . date('Y') . '!';

?>

Edit: Added logic to compensate for the '01' returned by date('W');

Answer 5

echo getLastWeekOfYear(2015);

function getLastWeekOfYear($year) {
    $date = new DateTime();
    return date('W', strtotime(date('Y-m-d', strtotime($date->setISODate($year, 1, "1")->format('Y-m-d') . "-1day"))));
}

Answer 6

With strtotime() you can count till 2037 cause the 2038 bug

To be sure to count all weeks of a year you must count from the 28th December, because is the only day surely in the last week of the year.

<?php
for($year=2018;$year<2038;$year++) {
    echo $year.' => ' .date("W",strtotime('28th December '.$year)) .' Weeks<br>';
}
?>

Result:

• 2018 => 52 Weeks
• 2019 => 52 Weeks
• 2020 => 53 Weeks
• 2021 => 52 Weeks
• 2022 => 52 Weeks
• 2023 => 52 Weeks
• 2024 => 52 Weeks
• 2025 => 52 Weeks
• 2026 => 53 Weeks
• 2027 => 52 Weeks
• 2028 => 52 Weeks
• 2029 => 52 Weeks
• 2030 => 52 Weeks
• 2031 => 52 Weeks
• 2032 => 53 Weeks
• 2033 => 52 Weeks
• 2034 => 52 Weeks
• 2035 => 52 Weeks
• 2036 => 52 Weeks
• 2037 => 53 Weeks