php 计算两个日期这间的间隔天数

function daysbetweendates($date1, $date2){
    $date1 = strtotime($date1);
    $date2 = strtotime($date2);
    $days = ceil(abs($date1 - $date2)/86400);
    return $days;
}

<?php
functionmaketime($date)
{
list($year,$month,$day) = explode('-',$date);
returnmktime(0,0,0,$month,$day,$year);
}
$date1 = '2007-01-08';
$date2 = '2007-03-01';
$d = (maketime($date2) - maketime($date1)) / (3600*24);
echo'相差$d 天';

?>

if (defined('CONST_NAME')) {
    //do something 
}

if (isset($var_name)) {
    //do something
}

函数检测用function_exists，注意待检测的函数名也需要使用引号，如：

if (function_exists('fun_name')) {
 fun_name();
}

<?php
/* 判断常量是否存在*/
if (defined('MYCONSTANT')) {
echo MYCONSTANT;
}
//判断变量是否存在
if (isset($myvar)) {
echo "存在变量$myvar.";
}
//判断函数是否存在
if (function_exists('imap_open')) {
echo "存在函数imag_openn";
} else {
echo "函数imag_open不存在n";
}
?>

<?php
/**
 *  计算.生肖
 * 
 * @param int $year 年份
 * @return str
 */
function get_animal($year){
    $animals = array(
            '鼠', '牛', '虎', '兔', '龙', '蛇', 
            '马', '羊', '猴', '鸡', '狗', '猪'
    );
    $key = ($year - 1900) % 12;
    return $animals[$key];
}

echo get_animal(1990);    // 马
echo get_animal(2010);    // 虎

<?php
/**
 *  计算.星座
 *
 * @param int $month 月份
 * @param int $day 日期
 * @return str
 */
function get_constellation($month, $day){
    $signs = array(
            array('20'=>'宝瓶座'), array('19'=>'双鱼座'),
            array('21'=>'白羊座'), array('20'=>'金牛座'),
            array('21'=>'双子座'), array('22'=>'巨蟹座'),
            array('23'=>'狮子座'), array('23'=>'处女座'),
            array('23'=>'天秤座'), array('24'=>'天蝎座'),
            array('22'=>'射手座'), array('22'=>'摩羯座')
    );
    $key = (int)$month - 1;
    list($startSign, $signName) = each($signs[$key]);
    if( $day < $startSign ){
        $key = $month - 2 < 0 ? $month = 11 : $month -= 2;
        list($startSign, $signName) = each($signs[$key]);
    }
    return $signName;
}

echo get_constellation(12, 11);    // 射手座
echo get_constellation(6, 6);      // 双子座

$header = get_headers($url, 1);
if (strpos($header[0], ’301′) || strpos($header[0], ’302′)) {
if (is_array($header['Location'])) {
return $header['Location'][count($header['Location'])-1];
} else {
return $header['Location'];
}
} else {
return $url;
}

<?php
//
echo get_redirect_url('http://www.111cN.nEt');
//输出结果为：http://code.google.com/android/
function get_redirect_url($url){
    $redirect_url = null;

    $url_parts = @parse_url($url);
    if (!$url_parts) return false;
    if (!isset($url_parts['host'])) return false; //can't process relative URLs
    if (!isset($url_parts['path'])) $url_parts['path'] = '/';

    $sock = fsockopen($url_parts['host'], (isset($url_parts['port']) ? (int)$url_parts['port'] : 80), $errno, $errstr, 30);
    if (!$sock) return false;

    $request = "HEAD " . $url_parts['path'] . (isset($url_parts['query']) ? '?'.$url_parts['query'] : '') . " HTTP/1.1rn";
    $request .= 'Host: ' . $url_parts['host'] . "rn";
    $request .= "Connection: Closernrn";
    fwrite($sock, $request);
    $response = '';
    while(!feof($sock)) $response .= fread($sock, 8192);
    fclose($sock);

    if (preg_match('/^Location: (.+?)$/m', $response, $matches)){
        if ( substr($matches[1], 0, 1) == "/" )
            return $url_parts['scheme'] . "://" . $url_parts['host'] . trim($matches[1]);
        else
            return trim($matches[1]);

    } else {
        return false;
    }

}

 function ip2number($ip)
      {

          $t = explode('.', $ip);
          $x = 0;
          for ($i = 0; $i < 4; $i++)

          {
              $x = $x * 256 + $t[$i];

          }
          return $x;

      }

function number2ip($num)

      {
          $t = $num;
          $a = array();

          for ($i = 0; $i < 4; $i++)
          {
              $x = $t % 256;
              if($x < 0) $x += 256;
              array_unshift($a, $x);
              $t = intval($t / 256);
          }
          return implode('.', $a);
 }