我将文本框的值（由用户插入）保存在变量$ no中。但是当我写一个回声时它并没有显示任何东西。我不明白为什么？
我相信我没有正确插入值。我想要一些帮助。 谢谢。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type"
content="text/html; charset=ISO-8859-1" />
<title>Attendence form</title>
<link type = "text/css" rel = "stylesheet" href = "style.css">
</head>
<body>
<form action = "<?php $_SERVER['PHP_SELF']; ?>" method = "post">
<table>
<tr>
<th>Department</th>
<th>Year</th>
<th>Course</th>
<th>Lecture No</th>
<th>Date</th>
</tr>
<tr>
<td>
<select name = "dept">
<option value = "cse">CSE</option>
<option value = "eee">EEE</option>
</select>
</td>
<td>
<select name = "year">
<option value = "1st">1st</option>
<option value = "2nd">2nd</option>
</select>
</td>
<td>
<select name = "course">
<option value = "cse2200">CSE 2200</option>
<option value = "cse2201">CSE 2201</option>
<option value = "cse2213">CSE 2202</option>
<option value = "eee2217">EEE 2217</option>
<option value = "math2207">MATH 2207</option>
</select>
</td>
<td>
<input type = "text" name = "days" />
</td>
<td>
<?php echo date("Y/m/d"); ?>
</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td>
<input type = "submit" name = "submit" value = "Take attendence" />
</td>
<td>
<input type = "submit" name = "view" value = "View Attendence" />
</td>
</tr>
</table>
<hr />
<table>
<?php
$year = $_POST['year'];
$dept = $_POST['dept'];
$course = $_POST['course'];
$no = $_POST['days'];
$date = date("Y/m/d");
echo $days;
if(isset($_POST['submit']) && !isset($_POST['calculate']) && !isset($_POST['view'])){
if($year == '1st')
$roll = 1400000;
else if($year == '2nd')
$roll = 1300000;
if($dept == 'cse')
$roll = $roll + 7000;
else if($dept == 'eee')
$roll = $roll + 3000;
$i = 1;
echo '<tr><th>Attendence Form:</th></tr>';
while($i <= 10){
$roll = $roll + 1;
echo '<tr> <td> <input type = "checkbox" value = "'. $roll . '" name = "present[]">'.$roll.'</input> </td></tr>';
$i++;
}
?>
<td>
<input type = "submit" name = "calculate" value = "Calculate" />
</td>
<?php
}
else if(isset($_POST['calculate'])){
$dbc = mysqli_connect('localhost', 'root', '', 'rankodatabase')
or die('Error connecting database');
foreach($_POST['present'] as $p){
$query1 = "SELECT * FROM attendence WHERE roll = '$p' AND course = '$course'";
$result1 = mysqli_query($dbc, $query1)
or die('Error in select query1');
$p_days = 0;
while($row = mysqli_fetch_array($result1)){
$p_days++;
echo 'roll'. $row['roll'] . ' course' . $row['course'] . ' date' . $row['date'] . ' percentage' . $row['percentage'] . '<br />';
}
echo 'Lecture' . $no;
/*$percentage = ($p_days / $no_of_lecture) * 100;
$query2 = "INSERT INTO attendence VALUES('$p', '$course', '$date', '$percentage')";
$result2 = mysqli_query($dbc, $query2)
or die('Error in insert query2'); */
}
//$query = "INSERT INTO attendence VALUES('"
}
?>
</table>
</form>
</body>
</html>