I hvae been working on this code for hours and can't figure out how to delete information from a database. It is currently claiming that result and checkbox aren't variables... I have looked at countless websites but can't seem to get this to work.
Thank you ahead of time.

    <head>
        <title>Lost Furry Friends</title>
        <link type="text/css" rel="stylesheet" href="LFF.css">
    </head>
    <body>

        <table border="0" width="100%">
            <tbody>
                <tr>
                    <td colspan="4"><div id="csl_site_title" ><br /><center>Lost Furry Friends (LFF) Program</center><br /></div></td>
                </tr>
                <tr>
                    <td width="25%"><center><div id="csl_navigation"><a href="intro.html">Introduction</a></div></center></td>
                    <td width="25%"><center><div id="csl_navigation"><a href="Lost.php">Lost</a></div></center></td>
                    <td width="25%"><center><div id="csl_navigation"><a href="Found.php">Found</a></div></center></td>
                    <td width="25%"><center><div id="csl_navigation"><a href="New_Entry.php">New Entry</a></div></center></td>
                </tr>
                <tr>
                    <td colspan="4">
                        <div id="csl_page_title">
                            <br /><p><center>Administration Page</center><p>
                            <center><br><input name="delete" type="submit" id="delete" value="Delete"></td><br></center>
                        </div>
                    </td>
                </tr>
            </tbody>
        </table>
        <table border="1" style="width:100%">
            <tr>
            <?php
    //Create a new mysqli connection
    @ $db = new mysqli('localhost', 'root', 'secret', 'Final');
    if ($db->connect_error) { 
        echo 'ERROR: Could not connect to database, error is '. $db->connect_error;
        exit;
    } 

    //Make a query against the MySQL server, and store that result
    //in resultset $res
    $res = $db->query("SELECT * FROM PET RIGHT JOIN Pet_Color USING (Pet_ID) 
        JOIN Color USING (Color_ID) 
        LEFT JOIN Species USING(Species_Number) 
        Left Join location using(PET_ID)");

    //Check to make sure the query succeeded 
    if (!$res) {
        echo $db->error . '<br/>';
        exit;
    }

    //Store the result in an associative array
    $result_array = $res->fetch_all(MYSQLI_ASSOC);

    //Create the table to report results
    ?>
        <table border="1">
            <tr>
                <td><b>Delete?</b></td>
                <td><b>ID</b></td>
                <td><b>Picture</b></td>
                <td><b>Name</b></td>
                <td><b>Colour</b></td>
                <td><b>Gender</b></td>
                <td><b>Behaviour</b></td>
                <td><b>Date</b></td>
                <td><b>Birthday</b></td>
                <td><b>Status</b></td>
                <td><b>Specie</b></td>
                <td><b>Address</b></td>
            </tr>
    <?php
    foreach ($result_array as $row){
        $i=0;
        ?>
            <tr>
                <td><input name="checkbox[]" type="checkbox" id="checkbox[]" value="<? echo $rows['Pet_ID']; ?>"></td>
                <td><?php echo $row['Pet_ID']?></td>
                <td><?php echo $row['Pet_Image']?></td>
                <td><?php echo $row['Pet_Name']?></td>
                <td><?php echo $row['Color_Description']?></td>
                <td><?php echo $row['Pet_Gender']?></td>
                <td><?php echo $row['Pet_Behavior']?></td>
                <td><?php echo $row['Pet_Date']?></td>
                <td><?php echo $row['Pet_Birthday']?></td>
                <td><?php echo $row['Pet_Status']?></td>
                <td><?php echo $row['Species_Name']?></td>
                <td><?php echo $row['Location_Address']?> <?php echo $row['Location_State']?>, <?php echo $row['Location_Zip']?></td>
            </tr>
        <?php
    }
    ?></table><?php
    if(isset($_POST['delete']))
{
    if(count($_POST['checkbox']) !=0)
    {
        $array = array("checkbox" => $_POST['checkbox']);
        $ids = implode(',', $array);
        $result = mysql_query("DELETE FROM $Pet WHERE Pet_ID IN($ids) ") or die(mysql_error());
    }
}
if($result){
echo "<meta http-equiv=\"refresh\" content=\"0;URL=delete_multiple.php\">";
}


    //Clean up
    $res->close();

    //Close the connection
    $db->close();
?>
            </tr>
        </table>
    </body>
</html>
      $result = mysql_query("DELETE FROM $Pet WHERE Pet_ID IN($ids) ") or die(mysql_error());
    }

    0r
          $result = mysqli_query("DELETE FROM $Pet WHERE Pet_ID IN($ids) ") or die(mysql_error());
    }

your missing the very important thing on your code

<form method="POST">

I would like to point out that one you cant POST your DATA without that command

joshuajames.delacruz, thanks for pointing that out. It is able to run through the code now without errors. However, it still isn't deleteing any of the rows.

    if(isset($_POST['delete']))
{
    if(count($_POST['checkbox']) !=0)
    {
        $array = array("checkbox" => $_POST['checkbox']);
        $ids = implode(',', $array);
        $result = $db->query("DELETE FROM Pet WHERE Pet_ID=($ids)") or die(mysql_error());
    }
}
if($result){
echo "<meta http-equiv=\"refresh\" content=\"0;URL=delete_multiple.php\">";
}


    //Clean up
    $res->close();

    //Close the connection
    $db->close();
?>

that should be on the upper part before the html codes
also i would like to change your query to this format if its ok with you
DELETE FROM Pet WHERE Pet_ID=$ids

Thanks!
It's deleteing now but for some reason it's taking out the entire table.

lets debug the code insert some data i think 3 is enough to know if its calling all the ids

comment this one for now

$result = $db->query("DELETE FROM Pet WHERE Pet_ID=($ids)") or die(mysql_error());

echo this one put this before the $result

echo $query = DELETE FROM Pet WHERE Pet_ID=$ids

Like this?

    if(isset($_POST['delete']))
    {
    if(count($_POST['checkbox']) !=0)
        {
        $array = array("checkbox" => $_POST['checkbox']);
        $ids = implode(',', $array);
        echo $db->$query = "DELETE FROM Pet WHERE Pet_ID=$ids";
        //$result = $db->query("DELETE FROM Pet WHERE Pet_ID=$ids") or die(mysql_error());
    }
}

just this

if(isset($_POST['delete']))
    {
    if(count($_POST['checkbox']) !=0)
        {
        $array = array("checkbox" => $_POST['checkbox']);
        $ids = implode(',', $array);
        //using this format makes it easy to identify the problems.
        //but when we echo it before the query you will notice all the id's
        //that will be inserted throug the query
        echo $query = "DELETE FROM Pet WHERE Pet_ID=$ids";

        // the echo result will be like this 
        //DELETE FROM Pet WHERE Pet_ID=1
       // DELETE FROM Pet WHERE Pet_ID=2

        //if we echo the result it will be [obj_some text]
        //$result = $db->query($query) or die(mysql_error());
    }
}

DELETE FROM Pet WHERE Pet_ID=Array is the result. This means it's not even getting the number correct? Would this flaw be with the checkbox then?

Currently the code is

    <head>
        <title>Lost Furry Friends</title>
        <link type="text/css" rel="stylesheet" href="LFF.css">
    </head>
    <body>
    <form method="POST">
        <table border="0" width="100%">
            <tbody>
                <tr>
                    <td colspan="4"><div id="Admin_site_title" ><br /><center>Lost Furry Friends (LFF) Program</center><br /></div></td>
                </tr>
                <tr>
                    <td width="25%"><center><div id="csl_navigation"><a href="intro.html">Introduction</a></div></center></td>
                    <td width="25%"><center><div id="csl_navigation"><a href="Lost.php">Lost</a></div></center></td>
                    <td width="25%"><center><div id="csl_navigation"><a href="Found.php">Found</a></div></center></td>
                    <td width="25%"><center><div id="csl_navigation"><a href="New_Entry.php">New Entry</a></div></center></td>
                </tr>
                <tr>
                    <td colspan="4">
                        <div id="csl_page_title">
                            <br /><p><center>Administration Page</center><p>
                            <center><br><input name="delete" type="submit" id="delete" value="Delete"></td><br></center>
                        </div>
                    </td>
                </tr>
            </tbody>
        </table>
        <table border="1" style="width:100%">
            <tr>
            <?php
    //Create a new mysqli connection
    @ $db = new mysqli('localhost', 'root', 'secret', 'Final');
    if ($db->connect_error) { 
        echo 'ERROR: Could not connect to database, error is '. $db->connect_error;
        exit;
    } 

    //Make a query against the MySQL server, and store that result
    //in resultset $res
    $res = $db->query("SELECT * FROM PET RIGHT JOIN Pet_Color USING (Pet_ID) 
        JOIN Color USING (Color_ID) 
        LEFT JOIN Species USING(Species_Number) 
        Left Join location using(PET_ID)");

    //Check to make sure the query succeeded 
    if (!$res) {
        echo $db->error . '<br/>';
        exit;
    }

    //Store the result in an associative array
    $result_array = $res->fetch_all(MYSQLI_ASSOC);


if(isset($_POST['delete']))
    {
    if(count($_POST['checkbox']) !=0)
        {
        $array = array("checkbox" => $_POST['checkbox']);
        $ids = implode(',', $array);
        //using this format makes it easy to identify the problems.
        //but when we echo it before the query you will notice all the id's
        //that will be inserted throug the query
        echo $query = "DELETE FROM Pet WHERE Pet_ID=$ids";
        // the echo result will be like this 
        //DELETE FROM Pet WHERE Pet_ID=1
       // DELETE FROM Pet WHERE Pet_ID=2
        //if we echo the result it will be [obj_some text]
        //$result = $db->query($query) or die(mysql_error());
    }
}
if($result){
echo "<meta http-equiv=\"refresh\" content=\"0;URL=delete_multiple.php\">";
}

    //Create the table to report results
    ?>
        <table border="1">
            <tr>
                <td><b>Delete?</b></td>
                <td><b>ID</b></td>
                <td><b>Picture</b></td>
                <td><b>Name</b></td>
                <td><b>Colour</b></td>
                <td><b>Gender</b></td>
                <td><b>Behaviour</b></td>
                <td><b>Date</b></td>
                <td><b>Birthday</b></td>
                <td><b>Status</b></td>
                <td><b>Specie</b></td>
                <td><b>Address</b></td>
            </tr>
    <?php


    foreach ($result_array as $row){
        $i=0;

        ?>
            <tr>
                <td><input name="checkbox[]" type="checkbox" id="checkbox[]" value="<? echo $rows['Pet_ID']; ?>"></td>
                <td><?php echo $row['Pet_ID']?></td>
                <td><?php echo $row['Pet_Image']?></td>
                <td><?php echo $row['Pet_Name']?></td>
                <td><?php echo $row['Color_Description']?></td>
                <td><?php echo $row['Pet_Gender']?></td>
                <td><?php echo $row['Pet_Behavior']?></td>
                <td><?php echo $row['Pet_Date']?></td>
                <td><?php echo $row['Pet_Birthday']?></td>
                <td><?php echo $row['Pet_Status']?></td>
                <td><?php echo $row['Species_Name']?></td>
                <td><?php echo $row['Location_Address']?> <?php echo $row['Location_State']?>, <?php echo $row['Location_Zip']?></td>
            </tr>
        <?php
    }

    ?></table><?php



    //Clean up
    $res->close();

    //Close the connection
    $db->close();
?>
            </tr>
        </table>
        </form>
    </body>
</html>

lets just focus on the delete function of your button no need to put all the codes

try this one: i havent tested it. please notify me about the warning or errors also the one really needed DELETE FROM Pet WHERE Pet_ID=Array

if(isset($_POST['delete']))
    {
        if(isset($_POST['checkbox'])){

            if (is_array($_POST['checkbox'])) {
                foreach($_POST['checkbox'] as $ids){
                  //get the values
                  echo $ids;
                  echo $query = "DELETE FROM Pet WHERE Pet_ID=$ids";
                }

            } else {
                //error
                $value = $_POST['checkbox'];
                echo $value;
            }
}
}

DELETE FROM Pet WHERE Pet_ID=
Notice: Undefined variable: result in C:\xampp\htdocs\Final_Project\Admin.php on line 74

These are the errors and prints that comes from the code:

if(isset($_POST['delete']))
    {
        if(isset($_POST['checkbox'])){
            if (is_array($_POST['checkbox'])) {
                foreach($_POST['checkbox'] as $ids){
                  //get the values
                  echo $ids;
                  echo $query = "DELETE FROM Pet WHERE Pet_ID=$ids";
                }
            } else {
                //error
                $value = $_POST['checkbox'];
                echo $value;
            }
}
}

sorry I notice that my code has errors

if(isset($_POST['delete']))
    {
        if(isset($_POST['checkbox'])){
            if (is_array($_POST['checkbox'])) {
                foreach($_POST['checkbox'] as $ids){
                  //get the values
                  echo $ids;
                  echo $query = "DELETE FROM Pet WHERE Pet_ID=$ids";
                }
            } else {
                //error
                //should be $ids not $value
                $ids = $_POST['checkbox'];
                echo $value;
            }
}
}

It still has the same results.
DELETE FROM Pet WHERE Pet_ID=
Is there a way to see what the checkbox is returning?

i tried this one but without the query it runs. i think your code about the checkbox values you can inspect the elements to know if it has value

<?php 
if(isset($_POST['delete']))
    {
        if(isset($_POST['checkbox'])){

            if (is_array($_POST['checkbox'])) {
                foreach($_POST['checkbox'] as $ids){
                  //get the values
                  echo $ids;
                }

            } else {
                //error
                $ids = $_POST['checkbox'];
                echo $ids;
                echo "error";
            }
}
}
 ?>

 <!DOCTYPE html>
 <html>
 <head>
     <title></title>
 </head>
 <body>
 <form method="POST">
    <input type="checkbox" name="checkbox[]" value="1">
    <input type="checkbox" name="checkbox[]" value="2">
    <input type="checkbox" name="checkbox[]" value="3">
    <input type="checkbox" name="checkbox[]" value="4">
    <input type="submit" name="delete">
 </form>
 </body>
 </html>