php wp_insert data on front using a form - php

Question

I'm using a form on my website to allow user to create posts on my wordpress admin.
It works fine, but I have an issue, I don't get the tags meta inside my admin.
here is my php code :
<?php
if(isset($_POST['submit'])){
$err = array();
$err['status'] = true;
$output = "";
if(empty($_POST['pseudo'])){
$err['status'] = false;
$err['msg'][] = 'Le champ "Pseudo" ne peut être vide.';
}
if(empty($_POST['mail']) || !preg_match('/[a-zA-Z0-9._-]+#[a-zA-Z0-9._-]+\.[a-zA-Z]{2,4}/',$_POST['mail'])){
$err['status'] = false;
$err['msg'][] = 'Le champs "Mail" est mal renseigné';
}
if(empty($_POST['title'])){
$err['status'] = false;
$err['msg'][] = 'Le champ "Titre" ne peut être vide.';
}
if(empty($_POST['content'])){
$err['status'] = false;
$err['msg'][] = 'Le champ "Article" ne peut être vide.';
}
if($err['status']){
$insert = array(
'post_status' => 'publish',
'post_title' => htmlentities($_POST['title']),
'post_content' => htmlentities($_POST['content']),
'post_category' => array(11),
'post_author' => 999,
);
$post_id = wp_insert_post($insert);
if($post_id != 0){
/*
TAGS
*/
if(!empty($_POST['keywords'])){
$keywords = explode(',',$_POST['keywords']);
foreach($keywords as $k=>$v){
$tag = trim(strip_tags($v));
wp_insert_term(
$tag,
'post_tag',
array(
'slug' => sanitize_title($tag)
)
);
}
}
$user_meta_values = array(
'pseudo' => htmlentities($_POST['pseudo']),
'mail' => $_POST['mail']
);
$output = add_post_meta($post_id, "user_meta", json_encode($user_meta_values)) ? 'Article inséré avec succès.' : 'Une erreur est survenue lors de l\enregistrement.' ;
}
}
else{
foreach($err['msg'] as $k=>$v)
$output .= $v . '<br />';
}
}
?>
my html form :
<form method="post" action="<?php echo site_url().'/ajouter'; ?>">
<p><label for="pseudo">Pseudo</label><input type="text" name="pseudo" id="pseudo" value="" /></p>
<p><label for="mail">Mail</label><input type="text" name="mail" id="mail" value="" /></p>
<p><label for="title">Titre</label><input type="text" name="title" id="title" value="" /></p>
<p><label for="content">Article</label><textarea name="content" id="content" rows="10" cols="15"></textarea></p>
<p><label for="keywords">Mots clés</label><input type="text" name="keywords" id="keywords" value="" /> ( séparez les mots clés par des virgules )</p>
<p><input type="submit" name="submit" value="enregistrer" /></p>
</form>
Anyone know what I'm doing wrong ? can't find out why it's not working,
thanks for your help