我试图将“$phone”存储在我的sql数据库中，但是如果在phpmyadmin中将列类型设置为“int”，则不会输入任何数据。一旦我将coulmn类型更改为“varchar”，就可以推送数据
在form.php中：

<fieldset>
   <input placeholder="Your Phone Number" type="text" name="phone" value="<?= $phone ?>" tabindex="4">
   <span class="error"><?= $phone_error ?></span>
</fieldset>

$phone在formprocess.php中声明：

$fname_error = $lname_error = $email_error = $phone_error = $job_error = $nameauth_error = $privacy_error = $decline_error = "";
$fname = $lname = $email = $phone = $message = $jobtitle = $nameauth = $success = $privacy = "";

if (empty($_POST["phone"])) {
$phone_error = "Phone is required";
  } else {
 $phone = test_input($_POST["phone"]);
 // check if e-mail address is well-formed
  if (!preg_match("/^(\d[\s-]?)?[\(\[\s-]{0,2}?\d{3}[\)\]\s-]{0,2}?\d{3} 
  [\s-]?\d{4}$/i",$phone)) {
  $phone_error = "Invalid phone number"; 
  }
 }`

if ($privacy == 'agree') {

if ($fname_error == '' and $lname_error == '' and $email_error == '' and $phone_error == '' and $privacy_error == '' and $nameauth_error == '' and $job_error == '') 
    {   
        $sql = "INSERT INTO data (phoneNo) VALUES ('$phone');";
        mysqli_query($con, $sql);
        $success = "Enjoy your game!!";
        $fname = $lname = $email = $phone = $message = $jobtitle = $nameauth = "";
    }   

} else if ($privacy == '') {
    $privacy_error = "Please Accept or Decline Our Policy";
} else if ($privacy == 'disagree') {
    $decline_error = "Please Accept Our Privacy Policy to Continue";
}   

}

如果phpmyadmin中的列数据类型是varchar，那么这段代码可以很好地工作，但是如果我使用int，代码就会中断
这与我将变量初始化为“”这使它成为varchar有关吗？
是否必须将int值初始化为=0？