Envois du formulaire plusieurs fois

<div style="background: #EFEFEF; padding: 30px 0"><div class="body-cont" align="center">
<h4 class="txt_majuscule" style="margin-bottom: 20px;"><?php echo $NEWSLETTER_TITRE; ?></h4>

<?php
$FR_Email 	= NULL;
$MSG_OK 	= NULL;
$MSG_NO 	= NULL;
$affiche 	= true;
 
if(isset($_POST['Envoyer'])){

foreach($_POST as $var=>$val){if(!is_array($val)){$$var = strip_tags($val);}else{while(list($arvar,$arval) = each($val)){$$var[$arvar] = strip_tags($arval);}}}
 
if($MSG_NO==""){
 $res = $pdo->query("SELECT Email FROM tb_newsletter_adresse WHERE Email='$FR_Email';"); $data = $res->fetch(PDO::FETCH_ASSOC);
 if($data!=0) {$MSG_NO.= $NEWSLETTER_MSG_NO;}
 
 if($data==0)
 {
 $FR_Source = PAGE;
 $FR_Pays = $PAYS_ISO_2;
 $req_fr = $pdo->prepare ("INSERT INTO tb_newsletter_adresse (Email, Source, Pays) VALUES (:FR_Email, :FR_Source, :FR_Pays)");
 $req_fr ->execute(array("FR_Email"=>$FR_Email, "FR_Source"=>$FR_Source, "FR_Pays"=>$FR_Pays));
 $MSG_OK.= $NEWSLETTER_MSG_OK;
 $affiche = false;
 }
}
}
?>
<?php if ($affiche == true) { ?>

<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="multipart/form-data" name="Form1" autocomplete="off">
<div class="input-group mb-3 col-md-6">
<input type="email" class="form-control" placeholder="Veuillez entrez votre adresse mail" id="FR_Email" name="FR_Email" value="<?php echo $FR_Email; ?>" required >
<div class="input-group-append"><button class="btn btn-primary" type="submit" name="Envoyer"><i class="fa fa-paper-plane"></i></button></div>
</div>
</form>

<small class="form-text text-muted"><?php echo $NEWSLETTER_TEXTE; ?></small>

<?php } ?>
<?php if($MSG_OK){ ?><div class="div_20"></div><div class="alert alert-primary col-md-5" role="alert"><?php echo $MSG_OK; }?></div>
<?php if($MSG_NO){ ?><div class="div_20"></div><div class="alert alert-danger col-md-5" role="alert"><?php echo $MSG_NO; ?></div>
<?php } ?>
	
</div></div>