why use {} around vraiable?

[Lamp Lists <lamp.lists@xxxxxxxxx>]

hi,
I saw several times that some people use this
 
$parameters = array(
  'param1' => "{$_POST["param1"]}",
  'param2' => "{$_POST["param2"]}"
 );

or

 $query = mysql_query("SELECT * FROM table1 WHERE id='{$session_id}'");

I would use:

$parameters = array(
  'param1' => $_POST["param1"],
  'param2' => $_POST["param2"]
 );
 
 and

 $query = mysql_query("SELECT * FROM table1 WHERE id=' ".$session_id." ' ");


does it really matter? is there really difference or these are just two "styles"?

thanks.

-ll


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