how can I save all the data within a table with php

    <?php
    if (isset($_POST['buscar'])) {
        $grado=$_POST['grado'];
        $sec=$_POST['seccion'];
        $query="SELECT * FROM estudiante WHERE Grado='$grado' AND Seccion='$sec'";
        $resultado=$conexion->query($query);
        while ($row=$resultado-> fetch_assoc()) {
            $targeta=$row['CodigTarge']; ?>
            <tr>            
                <td class="center" ><input type ="text" readonly="readonly"  name="targeta" value="<?php echo $targeta; ?>"/></td>
                <td class="despla" ><?php echo $row['nombre']?><?php echo $row['apellido']?></td>
                <td class="mod"  >"><input type ="text" required name="nota" placeholder="salario" value=""/>
                </td>
            </tr>        
            <?php
        }
    } else {
            ?>
            <tr> <td class="center">ingrese grado y seccion</td></tr>
            <?php
        }
    ?>			     
</tbody>
</table>
<input  type = "submit" value="Guardar" name="Guardar"/>
<?php
if (isset($_POST['Guardar'])) {
        $resultado=[];
        $captura=array($_POST['targeta']=>$_POST["nota"]);
        foreach ($captura as $targeta=>$nota) {
            echo "su  numero de targeta es $targeta tine nota $nota.<br/>";
        }
    }

?>