Php,Warning: in_array() expects parameter 2 to be array, str

Bonjour,

j'ai un probleme avec mon code, quand j'envoi ça vient
Warning: in_array() expects parameter 2 to be array, string given in line 25


je suis debutant en php, aidez moi svp, en corrigeant mon code si possible

mon code de connexion

<?php
 $conn = mysqli_connect("localhost", "username", "password", "dbname");
 
 if(!$conn){
  die("Error: Failed to connect to database!");
 }
?>
<?php

 date_default_timezone_set("Etc/GMT+8");
 
 require_once 'conn.php';
 
 if(ISSET($_POST['upload'])){
  
  $file_name = $_FILES['image']['name'];
  $file_temp = $_FILES['image']['tmp_name'];
  $date_upload = date("Y-m-d");
  $allowed_ext = array("jpeg", "jpg", "gif", "png");
  $exp = explode(".", $file_name);
  $ext = end($exp);
  $path = "../es/uploads/".$file_name;
  $nome = !empty($_POST['nome']) ? $_POST['nome'] : NULL;  
  $mail = !empty($_POST['mail']) ? $_POST['mail'] : NULL;
  $numero = !empty($_POST['numero']) ? $_POST['numero'] : NULL;
  $nomeA = !empty($_POST['nomeA']) ? $_POST['nomeA'] : NULL;
  $formato = !empty($_POST['formato']) ? $_POST['formato'] : NULL;
  $categorie = !empty($_POST['categorie']) ? $_POST['categorie'] : NULL;
  $cadre = !empty($_POST['cadre']) ? $_POST['cadre'] : NULL;
  if(in_array($conn, $ext, $allowed_ext)){
   if(move_uploaded_file($file_temp, $path)){
    mysqli_query($conn, "INSERT INTO `image` VALUES('', '$file_name', '$date_upload', '$nome','$mail','numero','nomeA','formato','categorie','cadre')") or die(mysqli_error());
    echo "<center><h5 class='text-success'>Pedido enviado!!</h5></center>";
   }
  }else{
   echo "<center><h5 class='text-danger'>Erro, image legivel jpeg, jpg, png !</h5></center>";
  }
 }
?>

Edit: ajout des balises de code