echo preg_replace( "/([0-9]{2})-([0-9]{2})-([0-9]{4})/i", "$3-$2-$1", $date_a_convertir );
Juil 172013
echo preg_replace( "/([0-9]{2})-([0-9]{2})-([0-9]{4})/i", "$3-$2-$1", $date_a_convertir );
echo preg_replace( "/([0-9]{4})-([0-9]{2})-([0-9]{2})/i", "$3-$2-$1", $date_a_convertir );
echo preg_replace( "/([0-9]{2})\/([0-9]{2})\/([0-9]{4})/i", "$3/$2/$1", $date_a_convertir );
echo preg_replace( "/([0-9]{4})\/([0-9]{2})\/([0-9]{2})/i", "$3/$2/$1", $date_a_convertir );