You only put dot (.) if you want to concatenate a string. Please remove the dot since you are subtracting.
echo "Absent students: ";
echo floatval($row['all_studnets']) - floatval($row['current_studnets']);
echo "<br>";
Frage
i have simple db that it is filled by a form from a page, all is ok in the entry.
i have 2 fields in the database are: all_students and current_students filled by the user in the form that i want to calculate
the trick is that i am echoing only the latest db record in the output page.. to give me only the latest data inserted in the form...
now, i want to create a new field that give me the absent students automatically (all - current)
what i have tried, i read that i can NOT create a new calculated field in the db, it is not an excel, so i am trying to echo the calculation results of these 2 fields, to a new value that is the "absent students"
what you suggest? please help, here is my code
<?php
$con=mysqli_connect("localhost","root","PasswordHere","DBnameHere");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
$result = mysqli_query($con,"SELECT id, class, all_students, current_students FROM students ORDER BY id DESC LIMIT 1");
while($row = mysqli_fetch_array($result))
{
echo "Class: " . $row['class'] . "<br>";
echo "All students: " . $row['all_studnets'] . "<br>";
echo "Current students: " . $row['current_studnets'] . "<br>";
echo "Absent students: " . $row['all_studnets'] . - . $row['current_studnets'] . " <br>";
}
mysqli_close($con);
?>
Lösung
You only put dot (.) if you want to concatenate a string. Please remove the dot since you are subtracting.
echo "Absent students: ";
echo floatval($row['all_studnets']) - floatval($row['current_studnets']);
echo "<br>";
Andere Tipps
Try this line
echo "Absent students: " . $row['all_studnets'] - $row['current_studnets'] . " <br>";
Insted of this
echo "Absent students: " . $row['all_studnets'] . - . $row['current_studnets'] . " <br>";