PHP练手：日历（代码简单，扩展容易）

<?php
    class Calendar{
        public $weekarray = array('星期日','星期一','星期二','星期三','星期四','星期五','星期六');
        public $firstDay = '';//当月第一天
        public $firstNum = '';//返回当月第一天对应的星期数字
        public $firstDayNum = '';//当月第一天对应的中文星期
        
        /**
        *   指定日是星期几
        *   eg:$date='2014-07-21'
        */
        public function getWeek($date){
            $date = strtotime($date);//strtotime() 函数将任何英文文本的日期时间描述解析为 Unix 时间戳
            $num = date('w',$date);//数字型的星期几，如: "0" (星期日) 至 "6" (星期六)
            return $num;
        }

        /**
        *   取得指定月有多少天
        *   eg:$month = '2014-07'
        */
        public function getMonthNum($month){
            $month = strtotime($month);
            return date('t',$month);//指定月份的天数
        }
        
        /**
        *   显示日历
        */
        public function show(){
            //取得当前日期
            $year = date('Y');
            $month = date('m');
            $day = date('d');
            echo '<table border="1" style="text-align:center;">';
            echo '<tr><td colspan="7">'.$year.'-'.$month.'</td></tr>';
            echo '<tr><th>星期日</th><th>星期一</th><th>星期二</th><th>星期三</th><th>星期四</th><th>星期五</th><th>星期六</th></tr>';
            //取得当前月有多少天
            $yearMonth = '$year."-".$month';
            $monthNum = $this->getMonthNum($yearMonth);
            //取得当前月第一天是星期几
            $this->firstDay = $year."-".$month."-01";
            $this->firstNum = $this->getWeek($this->firstDay);
            $this->firstDayNum = $this->weekarray[$this->firstNum];
            
            echo '<tr>';
                for($i=1;$i<=$monthNum+($this->firstNum);$i++){
                    echo '<td>';
                    if($i >= $this->firstNum+1){
                        $a = $i-$this->firstNum;
                        if($a == $day){
                            echo '<p style="background-color:blue;color:#fff;">'.$a.'</p>';
                        }else{
                            echo '<p>'.$a.'</p>
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                        </a>
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                ';
                        }
                    }
                    echo '</td>';
                    if($i%7 == 0){//每输出7列就换一行
                        echo '</tr>';
                    }
                }
            echo '</table>';
        }

    }
    
    $calendar = new Calendar();
    $calendar->show();