Hello, i have this table events:

id_evento, evento_texto, evento_banner, evento_image, evento_cartaz, evento_idioma

Now i can upload the image to evento_banner and evento_image, because they're the same only changes the size (the code is "inside" the <form>):

<?php
     if(isset($_POST['Submit'])){
      //Declara um Array para armazenar a mensagem de erro
      $error = array();  

//se o nome for entregue
      if (empty($_POST['text'])){
       $error[] = "text miss";
      }else{
       $text=$_POST['text'];
      }

if (empty($_POST['cidade'])){
       $error[] = "cidade";
      }else{
       $cidade=$_POST['cidade'];
      }

      if (empty($_FILES["file"]["name"])){
       $error[] = "Choose an image for the band";
      }else{
       $image=$_FILES["file"]["name"];
      }


      //send to Database if there's no error '
      if (empty($error)) // If everything's OK...
      {
       $idioma=$_POST['idioma'];

       error_reporting(0);
       $change="";
       $abc="";
       define ("MAX_SIZE","2048");

       function getExtension($str){
        $i = strrpos($str,".");
        if (!$i) { return ""; }
        $l = strlen($str) - $i;
        $ext = substr($str,$i+1,$l);
        return $ext;
       }

       $errors=0;

       if($_SERVER["REQUEST_METHOD"] == "POST")
       {
        $uploadedfile = $_FILES['file']['tmp_name'];
        if ($image)
        {
         $filename = stripslashes($_FILES['file']['name']);
         $extension = getExtension($filename);
         $extension = strtolower($extension);
         if (($extension != "jpg") && ($extension != "jpeg") && ($extension != "png") && ($extension != "gif")){
          $change='<div class="notification n-error">Unknown Image extension </div> ';
          $errors=1;
         }else{
          $size=filesize($_FILES['file']['tmp_name']);
          if ($size > MAX_SIZE*1024){
           $change='<div class="notification n-error">You have exceeded the size limit!</div> ';
           $errors=1;
          }

          if($extension=="jpg" || $extension=="jpeg" ){
           $uploadedfile = $_FILES['file']['tmp_name'];
           $src = imagecreatefromjpeg($uploadedfile);
          }else if($extension=="png"){
           $uploadedfile = $_FILES['file']['tmp_name'];
           $src = imagecreatefrompng($uploadedfile);
          }else{
           $src = imagecreatefromgif($uploadedfile);
          }
          echo $scr;
          list($width,$height)=getimagesize($uploadedfile);
          $newwidth=900;
          $newheight=($height/$width)*$newwidth;
          $tmp=imagecreatetruecolor($newwidth,$newheight);
          $newwidth1=300;
          $newheight1=($height/$width)*$newwidth1;
          $tmp1=imagecreatetruecolor($newwidth1,$newheight1);
          imagecopyresampled($tmp,$src,0,0,0,0,$newwidth,$newheight,$width,$height);
          imagecopyresampled($tmp1,$src,0,0,0,0,$newwidth1,$newheight1,$width,$height);
          $filename = "../../images/bands/". $_FILES['file']['name'];

          $file=explode(".".$extension, $_FILES['file']['name']);

          $filename1 = "../../images/bands/".$file[0]."_small".".".$extension;

          imagejpeg($tmp,$filename,100);
          imagejpeg($tmp1,$filename1,100);
          imagedestroy($src);
          imagedestroy($tmp);
          imagedestroy($tmp1);
         }
        }
       }
       //If no errors registred, print the success message
       if(!$errors)
       {
        $image=explode('../', $filename);
         $image1=explode('../', $filename1);


         $insert=("INSERT INTO eventos(evento_texto, evento_cidade, evento_banner, evento_image, evento_idioma)
             VALUES ('".$text."', '".$cidade."', '", '".$image[2]."', '".$image1[2]."', '".$idioma."')");
         if(mysql_query($insert)){
          header('Location: eventos.php');
         }
         else{
          echo '<div class="notification n-error">'.mysql_error().'.</div>';
         }
        }
        else{
         echo '<div class="notification n-error">The band already exists!</div>';
        }
      }else{
       //If the "error" array contains error msg , display them
       echo '<div class="notification n-error" <ul>';
       foreach ($error as $key => $values)
       {
        echo '<li>'.$values.'</li>';
       }

       echo '</ul></div>';
      }
     }
     ?>

My goal is to add a different image to evento_cartaz.

Can someone help me?

Thank You

Add a separate file upload to your form, and process it apart from the other one.

Extra 1: you may wanna consider changing some coding habits, like giving your variables names that represent better what they do, so $tmp is $tmp_img and $tmp1is $tmp_event, same for $filename1 and $newwidth1.

Extra 2: explicitly telling your file input in the form that calls this php which file types you allow for upload may save you some code lines in the file type validation.