Valider un formulaire en jquery et php

Bonjour je crée un formulaire et je le valide en php et jquery
je voudrais valider les deux section du formulaire si l'utilisateur appuit sur oui sinon je valide juste la premiere section
j'arrive a afficher la deuxieme section quand l'utilisateur appuit sur oui mais je n'arrive pas valider le formulaire au complet, pourriez vous m'aider svp
voici mon code
HTML

<div class="wrap forms">
                <div class="row  pad-top">
                    <div class="col-md-4 col-md-offset-4 col-sm-6 col-sm-offset-3 col-xs-10 col-xs-offset-1">
                        <div class="panel panel-default" id="form">
                            <div class="panel-heading">
                                <strong>   Veillez vous inscrir ici </strong>  
                            </div>
                            <div class="panel-body">
                                <form role="form" id="enregistrer" method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" name="inscription">
                                    <br/>

                                    <div class="form-group input-group">
                                       <span class="input-group-addon"><i class="fa fa-tag"  ></i></span>
                                       <input  type="text" class="form-control" placeholder="Votre nom" name="nom" />
                                    </div>
                                    <span  class="error" style="color:red"><?php echo $nomErr; ?></span>
                                    <div class="form-group input-group">
                                        <span class="input-group-addon"><i class="fa fa-tag"  ></i></span>
                                        <input type="text" class="form-control" placeholder="Votre Prenom"  name="prenom"/>
                                        <span class="error"><?php echo $prenomErr; ?></span>
                                    </div> 
                                    <div class="form-group input-group">
                                        <span class="input-group-addon"><i class="fa fa-tag"  ></i></span>
                                        <input type="text" class="form-control" placeholder="Choisis nom utilisateur"  name="prenom"/>
                                        <span class="error"><?php echo $prenomErr; ?></span>
                                    </div> 
                                    <center>etes-vous pareiner par quelqu'un?
                                     <div class="btn-group">
                                        <button type="button" class="btn btn-default " id='oui' >oui</button>
                                        <button type="button" class="btn btn-default " id="non">non</button>
                                     </div><br/><br/>
                                    </center>

                                    <div class="parein">
                                            <div class="form-group input-group ">
                                                <span class="input-group-addon"><i class="fa fa-tag"  ></i></span>
                                                <input type="text" class="form-control " placeholder="Nom Parein"  name="nomP"/>
                                                <span class="error"><?php echo $nomPareinErr; ?></span>
                                            </div> 
                                        <div class="form-group input-group ">

JS
$(document).ready(function() {  
    
        $('.parein').hide();
        $('button[id="oui"]').on('click',function(){   
            $('.parein').slideDown('slow');
           /* $('input[name="nomF"]').prop('required',true);
            $('input[name="numero"]').prop('required',true);*/
  
        });
       
        $('button[id="non"]').on('click',function(){
              $('.parein').slideUp('slow');
        });
});

PHP
<?php
        require_once('dataBase.php');
        $data = new dataBase();
        $data->connecter();
        $nomErr = $prenomErr = $nomPareinErr = $nIdErr = $prenomPareinErr = "";;
        $nom = $prenom= $nomParein= $nId = $prenomParein="";
// define variables and set to empty values

        if ($_SERVER["REQUEST_METHOD"] == "POST") {
            if (!empty($_POST['ins-submit'])) {
                if (empty($_POST["nom"])) {

                    $nomErr = "* Veillez rentrer votre nom";
                } else {
                    $nom = ($_POST["nom"]);
                    // check if name only contains letters and whitespace
                    if (!preg_match("/^[a-zA-Z ]*$/", $nom)) {
                        $nomErr = "Only letters and white space allowed";
                    }
                }

                if (empty($_POST["prenom"])) {
                    $prenomErr = "* Veillez rentrer votre prenom";
                } else {
                    $prenom = ($_POST["prenom"]);
                    // check if name only contains letters and whitespace
                    if (!preg_match("/^[a-zA-Z ]*$/", $prenom)) {
                        $prenomErr = "Only letters and white space allowed";
                    }
                }

                
                if (empty($_POST["nomP"])) {
                    $nomPareinErr = "* Veillez rentrer le nom du Parein";
                } else {
                    $nomParein = ($_POST["nomP"]);
                    // check if name only contains letters and whitespace
                    if (!preg_match("/^[a-zA-Z ]*$/", $nomParein)) {
                        $nomPareinErr = "Only letters and white space allowed";
                    }
                }
                
                if (empty($_POST["prenomP"])) {
                    $prenomPareinErr = "* Veillez rentrer le prenom du Parein";
                } else {
                    $prenomParein = ($_POST["prenomP"]);
                    // check if name only contains letters and whitespace
                    if (!preg_match("/^[a-zA-Z ]*$/", $prenomParein)) {
                        $prenomPareinErr = "Only letters and white space allowed";
                    }
                }
                if (empty($_POST["numero"])) {
                    $nIdErr = "* Veillez rentrer le nom utilisateur du parein";
                }
}
?>
                                                <span class="input-group-addon"><i class="fa fa-tag"  ></i></span>
                                                <input type="text" class="form-control " placeholder="Prenom Parein"  name="prenomP"/>
                                                <span class="error"><?php echo $prenomPareinErr; ?></span>
                                         </div> 
                                            <div class="form-group input-group ">
                                                <span class="input-group-addon"><i class="fa fa-tag"  ></i></span>
                                                <input type="text" class="form-control" placeholder="Nom utilisateur"  name="numero"/>
                                                 <span class="error"><?php echo $nIdErr; ?></span>
                                            </div> 
                                    </div>
                                    <input type="submit" class="btn btn-info"  value="Valider" name="ins-submit">
                                </form>
                            </div>

                        </div>
  
                    </div>
                </div>
            </div>

EDIT: Ajout de la coloration syntaxique.