How to explode an array of strings and store results in another array (php)

Have text file in format:

(400, 530); 6.9; 5.7; 5.0;//------> continues for 100 values.

(500, 530); 7.9; 5.1; 5.0;

(600, 530); 6.7; 6.7; 7.2;

Code:

<?php
$file="./Speed10.asc";
$document=file_get_contents($file);
$rows = explode ('(', $document); //splits document into rows

foreach ($rows as &$rowvalue) {
     explode (';', $rowvalue);<----- How to assign each of these to member 
                                     of an array??
  }
}
?>

I'm trying to create 2D array, by splitting first into rows, then by element split by ';'