<input type="text" 将 id 值赋给 php 字符串

我有一个模态表单可以将员工工作时间戳写入 SQL 数据库。我从下拉菜单中选择员工，并使用 id 标签通过 javascript 函数填充姓名和姓氏输入框。当我提交表单时，数据使用 php 写入数据库。问题是我无法将 javascript 字符串转换为 php 字符串或将输入标签的 id 标签分配给 php 字符串。我知道在输入中写入我可以使用 php value="...." 分配值。

$nome = '<script>document.writeln(a);</script>'; 

不起作用

这里的代码

<div class="modal-body">
    <input type="hidden" name="edit_id" value="<?php echo $id; ?>">
    <div class="form-group">
        <label class="control-label col-sm-2" for="dipendente">Dipendente:</label>
        <div class="col-sm-4">
            <select id="dipendente" name="dipendente" onchange="nomeCognome()">
            <option value="dipendente">Seleziona dipendente</option>
            <?php 
                $sqlOperatore="SELECT nome, cognome FROM login ORDER BY nome ASC";
                $resultOperatore = $conn->query($sqlOperatore);
                    if ($resultOperatore->num_rows > 0) {                                    
                        while($row = $resultOperatore->fetch_assoc()) {
                            $nome = $row['nome'];
                            $cognome = $row['cognome'];
                            $dipendente = $nome . ' ' . $cognome;
            ?>                                                  
                <option><?php echo $dipendente; ?></option>
                        <?php } ?>                                                  
            </select>                                   
        </div>
                    <?php } ?>
        <label class="control-label col-sm-2" for=" "> </label>
        <div class="col-sm-4"></div>
    </div>                          
    <br>
    <div class="form-group">
        <label class="control-label col-sm-2" for="nome">Nome:</label>
        <div class="col-sm-4" id="nome">
            <input type="text" class="form-control" id="nome" name="nome" readonly> </div>
        <label class="control-label col-sm-2" for="cognome">Cognome:</label>
        div class="col-sm-4" id="cognome">
            <input type="text" class="form-control" id="cognome" name="cognome" readonly> </div>
    </div>                          
    <br>                                                        

    <script type="text/javascript">
        function nomeCognome() {
            var x = document.getElementById("dipendente").value;
            var [a, b, c] = x.split(' ');
            document.getElementById("nome").innerHTML = [a];
            document.getElementById("cognome").innerHTML = [b, c].join(' ');
        }
    </script>           
</div>
<div class="modal-footer">
    <button type="submit" class="btn btn-primary" name="add_item"><span class="glyphicon glyphicon-plus"></span> Aggiungi</button>
    <button type="button" class="btn btn-warning" data-dismiss="modal"><span class="glyphicon glyphicon-remove-circle"></span> Annulla</button>
</div> 

<?php
//Add Matricola  
if(isset($_POST['add_item'])){
    $edit_id = $_POST['edit_id'];
    $nome = $_POST['nome'];
    $cognome = $_POST['cognome'];                       
    $sql = "INSERT INTO gest_personale.timbratura (nome, cognome) 
                                           VALUES ('$nome', '$cognome')";
    if ($conn->query($sql) === TRUE) {
        echo '<script>window.location.href="visualizzaTimbrature.php"</script>';
    } else {
        echo "Errore: " . $sql . "<br>" . $conn->error;
    }   
}
?>

我收到以下错误/通知：通知：未定义索引：名称和通知：未定义索引：cognome