PHP Required fields (No HTML) - php

Question

So I need help with a required form field. I want the 3 fields (exam_id, subject, exam_date) to be required fields when filling out the PHP form. So when the insert button is hit, if a field is left blank and error will display or the action won't complete unless every field is filled in.
I'm using all php, no HTML and no, I don't want to redo my form as HTML calling the php, I want it like this. There's no security problems either, this is just a simple project.
My code:
<?php
echo '<link rel="stylesheet" type="text/css" href="css/tables.css" />';
$con = mysql_connect("localhost","root");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_select_db("StudentExams", $con);
if (isset($_POST['update']))
{
$UpdateQuery = "UPDATE Exam SET exam_id='$_POST[exam_id]', subject='$_POST[subject]', exam_date='$_POST[exam_date]' WHERE exam_id='$_POST[hidden]'";
mysql_query($UpdateQuery, $con);
};
if (isset($_POST['delete']))
{
$DeleteQuery = "DELETE FROM Exam WHERE exam_id='$_POST[hidden]'";
mysql_query($DeleteQuery, $con);
};
if (isset($_POST['insert']))
{
$InsertQuery = "INSERT INTO Exam (exam_id, subject, exam_date) VALUES ('$_POST[uexam_id]','$_POST[usubject]','$_POST[uexam_date]')";
mysql_query($InsertQuery, $con);
};
$sql = "SELECT * FROM Exam";
$Data = mysql_query($sql,$con);
echo "<table id='size' border='1'>
<tr>
<th>Exam_ID</th>
<th>Subject</th>
<th>Exam_Date</th>
</tr>";
while($record = mysql_fetch_array($Data))
{
echo "<form action=examisud.php method=post>";
echo "<tr>";
echo "<td>" . "<input type=text name=exam_id value=" . $record['exam_id'] . " </td>";
echo "<td>" . "<input type=text name=subject value=" . $record['subject'] . " </td>";
echo "<td>" . "<input type=text name=exam_date value=" . $record['exam_date'] . " </td>";
echo "<td>" . "<input type=hidden name=hidden value=" . $record['exam_id'] . " </td>";
echo "<td>" . "<input type=image name=update value=update id=submit src=images/update.png" . " </td>";
echo "<td>" . "<input type=image name=delete value=delete id=submit src=images/delete.png" . " </td>";
echo "</tr>";
echo "</form>";
}
echo "<form action=examisud.php method=post>";
echo "<tr>";
echo "<td><input type=text name=uexam_id></td>";
echo "<td><input type=text name=usubject></td>";
echo "<td><input type=text name=uexam_date></td>";
echo "<td>" . "<input type=image name=insert value=insert id=submit src=images/insert.png" . " </td>";
echo "</form>";
echo "</table>";
echo "<a href='ExamForm.html'> Back to main page </a>";
mysql_close($con);
?>
Thanks in advance for anyone who can help me out! I feel there is either a very simple solution i'm missing or it's very convoluted due to the absence of a generic HTML form.

Answer 1

Just do a check on the top with isset
if(!isset($_POST['exam_id'],$_POST['subject'],$_POST['exam_date']))
{
echo "These fields are required ! Please fill it up";
header("location:backtoform.php");exit;
}
Warning : Since you are passing the $_POST parameters directly onto your query, you are prone to SQL Injection attacks.
This(mysql_*) extension is deprecated as of PHP 5.5.0, and will be removed in the future. Instead, the MySQLi or PDO_MySQL extension should be used. Switching to PreparedStatements is even more better to ward off SQL Injection attacks !

Answer 2

isset( ... ) is only used to see if a field is set or not. It doesn't care if the value of the field is empty.
You need to use empty( .. ) instead. It would return true only if the field was ever set and is not empty. Two apples with one shot.
Across all your if statements, use !empty. Maintain an $error variable and initialize it to FALSE. Whenever an error occurs, set $error to TRUE.
In the end, perform the required operation only when $error == FALSE.
$error = false;
if ( !empty($_POST['update'] ){
// stuff
}
else {
// display error message
$error=true;
}
if(!$error){
// operations
}
This way you can neatly separate validations from operations.