Getting a Button to Display Query Results in PHP MYSQL

Question

I am trying to run a query that will display in my browser when I click the button, but instead the results are just displayed from the beginning. I have the button set to post and my php file as the action but it seems to just run the code from the beginning. Here is what I have:

<?php
$host = "localhost";
$db = "cis475";
$user = "root";
$pw = "";


$conn = new mysqli ($host, $user, $pw, $db);
if($conn->connect_error) die($conn->connect_error);

$readAllQuery = "SELECT * FROM enrollment JOIN course ON enrollment.CourseID 
= course.CourseID JOIN student ON enrollment.StudentID = student.StudentID";

    $result = $conn->query($readAllQuery);
    if (!$result) die($conn->error);

    echo "<table border='1'>";
    echo "<tr><td>EnrollmentID</td><td>Grade</td><td>EnrollmentSemester</td> 
   <td>CourseID</td><td>StudentID</td><td>Title</td><td>Credits</td> 
   <td>LastName</td><td>FirstMidName</td></tr>";
    while ($row = mysqli_fetch_assoc($result)){
        echo "<tr><td>{$row['EnrollmentID']}</td><td>{$row['Grade']}</td> 
   <td>{$row['EnrollmentSemester']}</td><td>{$row['CourseID']}</td><td> 
   {$row['StudentID']}</td><td>{$row['Title']}</td><td>{$row['Credits']} 
   </td> 
   <td>{$row['LastName']}</td><td>{$row['FirstMidName']}</td></tr>";

    }
echo "</table>";

?>

<form method='post' action='readAll.php'>

<input type='submit' name='submit' value='Show All Enrollments'>

</form>

Apps-n-Add-Ons · Accepted Answer · 2018-11-11 16:39:48Z

You need to see if 'something' is there (in this case, all you have is the submit) and then do the display....

<?php
if($_POST['submit']){
    $host = "localhost";
    $db = "cis475";
    $user = "root";
    $pw = "";

    $conn = new mysqli ($host, $user, $pw, $db);
    if($conn->connect_error) die($conn->connect_error);

    $readAllQuery = "SELECT * FROM enrollment JOIN course ON enrollment.CourseID = course.CourseID JOIN student ON enrollment.StudentID = student.StudentID";

    $result = $conn->query($readAllQuery);
    if (!$result) die($conn->error);

    echo "<table border='1'>";
    echo "<tr><td>EnrollmentID</td><td>Grade</td><td>EnrollmentSemester</td> 
    <td>CourseID</td><td>StudentID</td><td>Title</td><td>Credits</td> 
    <td>LastName</td><td>FirstMidName</td></tr>";
    while ($row = mysqli_fetch_assoc($result)){
        echo "<tr><td>{$row['EnrollmentID']}</td><td>{$row['Grade']}</td> 
        <td>{$row['EnrollmentSemester']}</td><td>{$row['CourseID']}</td><td> 
        {$row['StudentID']}</td><td>{$row['Title']}</td><td>{$row['Credits']} 
        </td><td>{$row['LastName']}</td><td>{$row['FirstMidName']}</td></tr>";
    }
    echo "</table>";
}
?>

<form method='post' action='readAll.php'>

<input type='submit' name='submit' value='Show All Enrollments'>

</form>

Jaswinder · Accepted Answer · 2018-11-13 11:31:46Z

Any code present in inside the program file will run upon execution, this is true for all languages, unless it is wrapped inside an if or any other conditional statements; in which case the code enclosed in the conditional statement will only be executed if the condition is true.

And thus to solve your issue, you'll need a conditional statement that checks if the form was submitted or not and if it was then execute the code that follows-

if(isset($_POST['submit'])){
    $host = "localhost";
    $db = "cis475";
    $user = "root";
    $pw = "";

    $conn = new mysqli ($host, $user, $pw, $db);
    if($conn->connect_error) die($conn->connect_error);

    $readAllQuery = "SELECT * FROM enrollment JOIN course ON enrollment.CourseID = course.CourseID JOIN student ON enrollment.StudentID = student.StudentID";

    $result = $conn->query($readAllQuery);
    if (!$result) die($conn->error);

    echo "<table border='1'>";
    echo "<tr><td>EnrollmentID</td><td>Grade</td><td>EnrollmentSemester</td> 
    <td>CourseID</td><td>StudentID</td><td>Title</td><td>Credits</td> 
    <td>LastName</td><td>FirstMidName</td></tr>";
    while ($row = mysqli_fetch_assoc($result)){
        echo "<tr><td>{$row['EnrollmentID']}</td><td>{$row['Grade']}</td> 
        <td>{$row['EnrollmentSemester']}</td><td>{$row['CourseID']}</td><td> 
        {$row['StudentID']}</td><td>{$row['Title']}</td><td>{$row['Credits']} 
        </td><td>{$row['LastName']}</td><td>{$row['FirstMidName']}</td></tr>";
    }
    echo "</table>";
}

In this snippet, we use if statement to check if variable $_POST['submit'] exists.
Here submit with is the name of your form's submit button
Note: a $_POST variable will only exist if the form was submitted, calling isset() will return false if the form wasn't submitted and as such your code inside { } will not be executed on first load but will run upon submit.

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