$search = array('{user}', '{site}');
$replace = array('Qiao', 'stackoverflow');
$subject = 'Hello {user}, welcome to {site}.';
echo str_replace ($search, $replace, $subject);
Results in Hello Qiao, welcome to stackoverflow..
$array_from_to = array (
'from1' => 'to1',
'from2' => 'to2'
);
This is not a two-dimensional array, it's an associative array.
Expanding on the first example, where we place the $search as the keys of the array, and the $replace as it's values, the code would look like this.
$searchAndReplace = array(
'{user}' => 'Qiao',
'{site}' => 'stackoverflow'
);
$search = array_keys($searchAndReplace);
$replace = array_value($searchAndReplace);
# Our subject is the same as our first example.
echo str_replace ($search, $replace, $subject);
Results in Hello Qiao, welcome to stackoverflow..