<?php
    $month = date("n");
    $today = date("j");
    if ($today >= 1 and $today <= 10){
        echo "今天是".$month."月".$today."日上旬";
    }elseif($today > 10 and $today <= 20){
        echo "今天是".$month."月".$today."日中旬";
    }else{
        echo "今天是".$month."月".$today."日下旬";
    }
    echo "<br>";
    $num = 1;
    $str = "10以内的偶数为:";
    while ($num <= 10){
        if ($num % 2 == 0){
            $str.=$num." ";
        }
        $num++;
    }
    echo $str;
    echo "<br>";
    $flag = 1;
    while ($flag != 1){
        echo "不会看到";
    }
    do{
        echo "会看到";
    }while ($flag != 1);
    echo "<br>";
    $sum = 1;
    for ($i = 1; $i <= 100; $i++){
        $sum *= $i;
    }
    echo "100! = ".$sum;
    echo "<br>";
    while (true){
        $tmp = rand(1,20);
        echo $tmp." ";
        if ($tmp == 10){
            echo "<p>变量等于10，终止循环";
            break;
        }
    }
?>