Probleme en upload php

Bonjour,

le code html est le suivant :


<form enctype="multipart/form-data" action="upload.php" method="POST">
<input type="hidden" name="MAX_FILE_SIZE" value="100000" />
Choose a file to upload: <input name="uploadedfile" type="file" /><br />
<input type="submit" value="Upload File" />
</form>

le code php:
<?php
$target_path = "/prepation/";
echo $_FILES['uploadedfile']['name'];
$target_path = $target_path . basename( $_FILES['uploadedfile']['name']);

if(move_uploaded_file($_FILES['uploadedfile']['tmp_name'], $target_path)) {
echo "The file ". basename( $_FILES['uploadedfile']['name']).
" has been uploaded";
} else{
echo "There was an error uploading the file, please try again!";
}
?>

le probléme c qu'il retourn tjr la valeur false aprés l'execution du fonction
move_uploaded_file veullez m'aider et merci d'avance