如何使用php回显从文本框表单发布的变量？

Question

update : You can understand my problem if you see my test link. http://smstostudents.com/rmk/index3.php (select any name and submit)

Here is my HTML form code

<input type="checkbox" name="student[]" value="1"><label>student name 1/label>
<input type="checkbox" name="student[]" value="2"><label>student name 2</label>
<input type="checkbox" name="student[]" value="3"><label>student name 3</label>

<textarea id="message" class="input" name="message" rows="7" cols="50">
Dear $studentname you have not paid the fees, please pay it as soon as possible.
</textarea><br />

The Php code is as follows.

<?php
$message = $_POST['message'];
$servername = "localhost";
$dbusername = "xxxxxx";
$dbpassword = "xxxxxxx";
$dbname = "xxxxxxxx";
foreach($_POST['student'] as $value)
{
    // Create connection
    $conn = new mysqli($servername, $dbusername, $dbpassword, $dbname);
    // Check connection
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }
    $getID = mysqli_fetch_assoc(mysqli_query($conn, "SELECT firstname, email FROM Students WHERE id = $value"));
    $studentname = $getID['firstname'];
    $email = $getID['email'];
    echo $message;
}
?>

What I am trying to achieve is, in the form text box "$studentname" will be replaced by student's name from the database. But echo $message doesn't display the students name, instead it just displays,

"Dear $studentname you have not paid the fees, please pay it as soon as possible."

how can I replace the "$studentname" by the Student's name. Sorry if it is easy, but I am stuck. Sorry, my English is bad, and I am a beginner in coding.

Update :

Actually i have no problem in the form. The form correctly posts the values to php. But, the textbox value contains "$studentname", which must be replaced with the student's name which is taken from the Database. But, the php code is not doing it, it is juts diplaying the textbox content as it is.

Thanks in advance.

Answer 1

First, you are connecting to the database inside a foreach loop... this is bad, and will make your script slower. Try moving the connection outside of the loop.

Second, you are querying the database multiple times for data you want to gather from a single table. There is an easier way to do this.

Here is an example:

<?php


$message = $_POST['message'];
$servername = "localhost";
$dbusername = "smstobdc_smstest";
$dbpassword = "removable";
$dbname = "smstobdc_smstest";

// Create connection
$conn = new mysqli($servername, $dbusername, $dbpassword, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
//First we need to sanitize the values. or you will be open to a mysql injection...
$students = array_map('mysql_real_escape_string',$_POST['students']); // this sanitizes all values inside $_POST['students'];
//now let's prepare them for the query
$students = "'".implode("','",$students)."'"; //this formats it like so: '1','2','3','4'....
//now let's perform our query.. if you want to fetch all the results, then loop like this...
//Make sure you perform the query and save the result resource so you can catch an error like so...
$result = mysqli_query($conn, 'SELECT `firstname`, `email` FROM `Students` WHERE `id` IN ('.$students.')')
//The actual query looks like this:
//    SELECT `firstname`, `email` FROM `Students` WHERE `id` IN ('1','2','3','4','5','6'[,etc..])

//now we can iterate through the results for each student. This while loop will continue until all the data specified by your student id's is returned
while($getID = mysqli_fetch_assoc($result)) {

    $studentname = $getID['firstname'];
    $email = $getID['email'];   

    //NOTE: $studentname in $message is literally "$studentname". PHP will not treat this as a variable... what you can do is replace the text...
    echo str_replace('$studentname',$studentname,$message);
}
?>

If you just want the quick and dirty way to do it with your code then here is that as well:

<?php


$message = $_POST['message'];
$servername = "localhost";
$dbusername = "smstobdc_smstest";
$dbpassword = "removable";
$dbname = "smstobdc_smstest";



foreach($_POST['student'] as $value) {

// Create connection
$conn = new mysqli($servername, $dbusername, $dbpassword, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$getID = mysqli_fetch_assoc(mysqli_query($conn, "SELECT firstname, email FROM Students WHERE id = $value"));
$studentname = $getID['firstname'];
$email = $getID['email'];   

    echo str_replace('$studentname',$studentname,$message);

}
?>