У меня есть страница contact.php, работающая на моем действующем веб-сайте, но даже когда посетитель вводит неполный текст в поля имени, адреса электронной почты или сообщения, форма считает их правильными и отображает сообщение об успешном завершении.

Как я могу указать такие вещи, как имя должно состоять минимум из 6 букв, электронная почта должна иметь символ @ и правильное окончание .com, .org и т. д.; и сообщение должно состоять не менее чем из 20 букв.

СЦЕНАРИЙ PHP

<?php

if ($_POST['submit']) {

  if (!$_POST['firstname']) {
    $error = "<br/>- Please enter your first name";
  }
  
  if (!$_POST['lastname']) {
    $error = "<br/>- Please enter your last name";
  }

  if (!$_POST['email']) {
    $error. = "<br/>- Please enter your email";
  }
  if (!$_POST['message']) {
    $error. = "<br/>- Please enter a message";
  }
  if (!$_POST['check']) {
    $error. = "<br/>- Please confirm you are human";
  }
  
  if ($error) {
    $result='<div class = "alert alert-danger" role = "alert">
    <strong>Whoops, there is an error</strong>. Please correct the following: '.$error.'</div>';
  } else {
    mail("[email protected]", 
   "Contact message", 
    "Name: ".$_POST['name']."
    Email: ".$_POST['name']."
    Message: ".$_POST['message']);
    
    {
    $result='<div class = "alert alert-success" role = "alert">Thank you, I\'ll be in touch shortly. </div>';
    }
  }
}
?>

#HTML CODE#

  <form method = "post" role = "form">
            <div class = "row">
            <div class = "col-md-3"></div>
                  <div class = "contact-icon">
                      <i class = "fas fa-user"></i>
                  </div>

                  <div class = "form-inline">
                    <div class = "col-md-9 form-group">
                          <label for = "name">your name</label>
                          <span class = "fieldSpan">
                          <input type = "text" 
                          name = "name" 
                          id = "input-field-name"
                          class = "form-control" 
                          placeholder = "your name" 
                          value = "<?php echo $_POST['name']; ?>"> 
                    </div>
                </div>
            </div>

        <div class = "row">
        <div class = "col-md-3"></div>
              <div class = "contact-icon">
                <i class = "fas fa-envelope"></i>
              </div>

              <div class = "form-inline">
              <div class = "col-md-9 form-group">
                      <label for = "email">your email address</label>
                      <span class = "fieldSpan">
                      <input type = "email" 
                      name = "email" 
                      id = "input-field-email"
                      class = "form-control" 
                      placeholder = "[email protected]" 
                      value = "<?php echo $_POST['email']; ?>">
                  </div>
                </div>
         </div>

        <div class = "row">
        <div class = "col-md-3"></div>
              <div class = "contact-icon">
                  <i class = "fas fa-pencil-alt"></i>
              </div>
        
              <div class = "form-inline">
                 <div class = "col-md-9 form-group">
                        <label for = "message">your message</label>
                        <span class = "fieldSpan vertical-align:top">
                        <textarea name = "message" 
                        rows = "5" 
                        id = "input-field-message"
                        class = "form-control" 
                        placeholder = "your message">
                        <?php echo $_POST['message']; ?></textarea>
                        <br>
                        <br>
                    </div>
                    </div>
              </div>
        </div>
 

              <div class = "col-md-12">
                 <div class = "checkbox">
                    <label>
                        <input type = "checkbox" 
                        name = "check"> 
                        Check this box if you're human.
                      </label>
                  </div>
              </div>
        </div>

      <div class = "col-md-3"></div>
      <div class = "row">
          <div class = "col-md-9">
              <input type = "submit" 
              name = "submit" 
              class = "btn btn-secondary" 
              value = "send message"/>
            </div> 
        </div>

     </form>
      
     </div>
      </div>
    </div>
  </section>
  

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