$re = '/SPECGRID([\s\S]*?)\//';
$str = 'MAPAXES -- Generated : Petrel
159589.61 7782837.94 159589.61 7783837.94 160589.61 7783837.94 /
GRIDUNIT -- Generated : Petrel
METRES /
SPECGRID -- Generated : Petrel
3 26 120 1 F /
COORDSYS -- Generated : Petrel
1 120 /
';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php