Php 在插入期间获取数据库中的空值
我有一个下拉列表框，其中有素食、非素食和高级素食餐厅选项。只要我选择一种类型，就会显示相应的宿舍录取号、学生姓名和天数（必须由用户输入的文本字段）（从登记表中）。我想将显示的字段插入名为“student_month”的表中。当我尝试插入时，会将空值插入student_month表中。我已将代码粘贴在下面，请查看。如有任何帮助，将不胜感激。非常感谢Php 在插入期间获取数据库中的空值,php,mysql,Php,Mysql,我有一个下拉列表框，其中有素食、非素食和高级素食餐厅选项。只要我选择一种类型，就会显示相应的宿舍录取号、学生姓名和天数（必须由用户输入的文本字段）（从登记表中）。我想将显示的字段插入名为“student_month”的表中。当我尝试插入时，会将空值插入student_month表中。我已将代码粘贴在下面，请查看。如有任何帮助，将不胜感激。非常感谢 <?php $q=$_GET['messtype']; echo "<html> <head>
<?php
$q=$_GET['messtype'];
echo "<html>
<head>
<form action='testbill.php' method='GET'>
<p><select name='messtype' id='Select1'>
<option value='1'>VEG</option>
<option value='2'>NON-VEG</option>
<option value='3'>SENIOR VEG MESS</option>
<p></select> </b>
<p><input type='submit'style='width:100;height:35' name='submit' value='Display details'>
</form>";
print "<div id='txtHint' align='center'><b>List of Student Details</b></div>";
if($q=='1')
{
$a=$_POST['hosteadmissionno'];
$b=$_POST['student_name'];
$con = mysql_connect('localhost', 'root', '');
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("hostel", $con);
$a1="SELECT hosteladmissionno,student_name,semester FROM registration WHERE mess_type = 'VEG' AND status_flag=1";
$a2="INSERT into student_month(hosteladmissionno,student_name) values('$a','$b')";
$result = mysql_query($a1,$con);
$final=mysql_query($a2,$con);
echo "<table border='1' width=80%>
<tr>
<th width=5%> S.No</th>
<th width=10%>H.Admin No</th>
<th width=10%>Student Name</th>
<th width=5%>No of Days</th>
</tr>";
$i=0;
while($row = mysql_fetch_array($result))
{
$i=$i+1;
echo "<form action='testbill.php' method='POST'>";
echo "<tr>";
echo "<td align=center>" .$i."</td>";
echo "<td size=10 align=center>" . $row['hosteladmissionno'] . "</td>";
echo "<td size=35 align=center>" . $row['student_name'] . "</td>";
echo "<td align=center>"."<input type='text' name='days_mess' size=2>".$row['days_mess']. "</td> ";
echo "</tr>";
}
echo "</table>";
mysql_close($con);
}
if($q=='2')
{
$con = mysql_connect('localhost', 'root', '');
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("hostel", $con);
$a1="SELECT hosteladmissionno,student_name,semester FROM registration WHERE mess_type = 'NON-VEG' AND status_flag=1";
$a2="INSERT into student_month(hosteladmissionno,student_name) values('$a','$b')";
$result = mysql_query($a1,$con);
$final=mysql_query($a2,$con);
echo "<table border='1' width=80%>
<tr>
<th width=5%> S.No</th>
<th width=10%>H.Admin No</th>
<th width=10%>Student Name</th>
<th width=5%>No of Days</th>
</tr>";
$i=0;
while($row = mysql_fetch_array($result))
{
$i=$i+1;
echo "<form action='testbill.php' method='POST'>";
echo "<tr>";
echo "<td align=center>" .$i."</td>";
echo "<td size=10 align=center>" . $row['hosteladmissionno'] . "</td>";
echo "<td size=35 align=center>" . $row['student_name'] . "</td>";
echo "<td align=center>"."<input type='text' name='days_mess' size=2>".$row['days_mess']. "</td> ";
echo "</tr>";
}
echo "</table>";
mysql_close($con);
}
if($q=='3')
{
$con = mysql_connect('localhost', 'root', '');
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("hostel", $con);
$a1="SELECT hosteladmissionno,student_name,semester FROM registration WHERE mess_type = 'SENIOR-VEG-MESS' AND status_flag=1";
$a2="INSERT into student_month(hosteladmissionno,student_name) values('$a','$b')";
$result = mysql_query($a1,$con);
$final=mysql_query($a2,$con);
echo "<table border='1' width=80%>
<tr>
<th width=5%> S.No</th>
<th width=10%>H.Admin No</th>
<th width=10%>Student Name</th>
<th width=5%>No of Days</th>
</tr>";
$i=0;
while($row = mysql_fetch_array($result))
{
$i=$i+1;
echo "<form action='testbill.php' method='POST'>";
echo "<tr>";
echo "<td align=center>" .$i."</td>";
echo "<td size=10 align=center>" . $row['hosteladmissionno'] . "</td>";
echo "<td size=35 align=center>" . $row['student_name'] . "</td>";
echo "<td align=center>"."<input type='text' name='days_mess' size=2>".$row['days_mess']. "</td> ";
echo "</tr>";
}
echo "</table>";
mysql_close($con);
}
if($result!='')
{
echo "<form action='testbill.php'>
<input type='submit' style='width:100;height:35'name='submit' value='calculate' /> </form>";
}
print "</html>";
?>
变量“$a”和“$b”不会从查询字符串中转义：
$a2="INSERT into student_month(hosteladmissionno,student_name) values('$a','$b')";
应该是：
$a2="INSERT into student_month(hosteladmissionno,student_name) values('".$a."','".$b."')";
使用IDE的语法突出显示来帮助您（请参见上面的差异）。；） 在这种情况下：默认调试顺序：1。检查查询字符串（echo$a1；）2。如果每个查询都正确，则应该有一个PHPMyAdmin（-like）数据库管理系统来将查询粘贴到其中。3.它是否表示查询执行正确？检查插入代码。