Button not being called with isset() function

Question

I'm having some trouble trying to build a very simple inventory management system. What I'm doing is showing the data from a database in a html table and in each row a create two buttons: one to edit and one to delete the item. The problem is that I'm not being able to call these buttons with the isset() function and I can't understand why. I've tried to create a specific function for these but still doesn't work. Anybody has any idea?

Here is the code:

P.S.: Don't mind small english erros or a lack of of brackets. I had to change the code a little bit.

 function searchTablet(){
    
      if(isset($_POST['btnSearchTablet'])){
            
            global $connection;

            $query="SELECT * FROM tablet";
            $run=mysqli_query($connection, $query);
            echo "<table class='table table-striped'>";
                echo "<thead>";
                    echo "<tr>";
                        echo "<th>ID</th>";
                        echo "<th>Brand</th>";
                        echo "<th>Model</th>";
                        echo "<th>Color</th>";
                        echo "<th>Price</th>";
                        echo "<th>Fabrication Date</th>";
                        echo "<th>Provider</th>";
                        echo "<th>Registration Date</th>";
                        echo "<th>Edit</th>";
                        echo "<th>Delete</th>";
                    echo "</tr>";
                echo "</thead>";  
                while($obj=mysqli_fetch_object($run)){
                    echo "<tr>";
                        echo "<td>$obj->id</td>";
                        echo "<td>$obj->idBrand</td>";
                        echo "<td>$obj->idModel</td>";
                        echo "<td>$obj->idColor</td>";
                        echo "<td>$obj->price</td>";
                        echo "<td>$obj->fabricationDate</td>";
                        echo "<td>$obj->idProvider</td>";
                        echo "<td>$obj->registrationDate</td>";
                        echo "<td><a href='resultTablet.php?btnEditTablet{$obj->id}'class='btn btn-primary' name='btnEditTablet'>Alterar</a></td>";
                        echo "<td><a href='resultTablet.php?btnDeleteTablet{$obj->id}' class='btn btn-danger' name='btnDeleteTablet'>Excluir</a></td>";
                    echo "</tr>";

                    if(isset($_POST["btnDeleteTablet{$obj->id}"])){   
                        $idTablet=$obj->id;
                        $delQuery="DELETE FROM tablet WHERE id='$idTablet'";
                        $delRun=mysqli_query($connection, $delQuery);
                        if($delRun){
                            echo "<div class='alert alert-success' role='alert'>Device was successfuly deleted.</div>";
                        }else{
                            echo "<div class='alert alert-danger' role='alert'>Error.</div>";
                        }    
                    }
}
                    

Answer 1

As always... looks like StackOverflow users are toxic and unfriendly and don't even try to help new people who want to get into programming.

So I will try to help you a little bit.

If you are passing parameters via URL you have to use $_GET not $_POST method.

Also, I would change

<a href='resultTablet.php?btnEditTablet{$obj->id}'class='btn btn-primary' name='btnEditTablet'>Alterar</a>

to

<a href='resultTablet.php?btnEditTablet={$obj->id}'class='btn btn-primary' name='btnEditTablet'>Alterar</a>

So you could do this:

if(isset($_GET["btnDeleteTablet"])){  

and you would get id via $_GET like this:

$idTablet=$_GET["btnDeleteTablet"];

After this change, you can close while loop you used before this if(isset($_GET["btnDeleteTablet"])) line,
also you wont need $obj->id anymore, because you will $_GET data decoupled from while loop or any other code you wrote before.

On another note, I see you forgot <tbody> </tbody> in your table.

EDIT:

Also, what are you doing with

 if(isset($_POST['btnSearchTablet'])){

This wont work after delete button click.

You shouldn't use it like that, because after the delete button click your page will go to URL with $_GET parameters and that if logic will prevent

 if(isset($_GET["btnDeleteTablet"])){  

logic working. So move whole

if(isset($_GET["btnDeleteTablet"])){  
...
}

out of if(isset($_POST['btnSearchTablet'])){

Read up about $_POST and $_GET methods also, read about forms you really need it.

Also, I recommend you to get program to profile requests so you could see how post and get data moves. I recommend you to install Fiddler program, so you would be able to see how post, get data moves.

Ok, I will try to fix your code at last so it could work:

<?php

function searchTablet(){
    global $connection;
    if(isset($_GET['btnDeleteTablet'])){
        deleteTablet();
    }
    //I dont why are you using it so I commented it out. 
    //if(isset($_POST['btnSearchTablet'])){
    //}
    
    displaySearchTablet();
}

function displaySearchTablet(){
    global $connection;

    $query      = "SELECT * FROM tablet";
    $run        = mysqli_query($connection, $query);

    while($obj = mysqli_fetch_object($run)){
        //Combine all rows into one variable
        $table_rows .= "
        <tr>
            <td>{$obj->id}</td>
            <td>{$obj->idBrand}</td>
            <td>{$obj->idModel}</td>
            <td>{$obj->idColor}</td>
            <td>{$obj->price}</td>
            <td>{$obj->fabricationDate}</td>
            <td>{$obj->idProvider}</td>
            <td>{$obj->registrationDate}</td>
            <td>
                <a href='resultTablet.php?btnEditTablet={$obj->id}' class='btn btn-primary' name='btnEditTablet'>Alterar</a>
            </td>
            <td>
                <a href='resultTablet.php?btnDeleteTablet={$obj->id}' class='btn btn-danger' name='btnDeleteTablet'>Excluir</a>
            </td>
        </tr>";
    }
    $result_table =
    "<table class='table table-striped'>
        <thead>
            <tr>
                <th>ID</th>
                <th>Brand</th>
                <th>Model</th>
                <th>Color</th>
                <th>Price</th>
                <th>Fabrication Date</th>
                <th>Provider</th>
                <th>Registration Date</th>
                <th>Edit</th>
                <th>Delete</th>
            </tr>
        </thead>
        <tbody>
            $table_rows
        </tbody>
    </table>";
    echo $result_table;
}
function deleteTablet(){
    global $connection;
    
    $id    = $_GET['btnDeleteTablet'];
    $query = "DELETE FROM tablet WHERE id = '$id'";
    $run   = mysqli_query($connection, $query);
    
    if($run){
        echo "<div class='alert alert-success' role='alert'>Device was successfuly deleted.</div>";
    }else{
        echo "<div class='alert alert-danger' role='alert'>Error.</div>";
    }
}

I kept it very basic, so you would be able to understand. I didn't pass parameters or returned anything so it would be more understandable to you.

Good luck on your journey to programming.

Answer 2

isset() will return false if an empty string is being submitted, so try using !empty() instead.