$re = '/(?<hora>[0-9]{8})\s(?<mix>\d{3})(?<resp>[I|O])/';
$str = ' 09523744 865O F010@@@@Y1905A46100000002 00000000151100157600STD20001
865O 030202040005 1029 003047100000000012602
865O 00000000000000000000000000000000000000000000517712002534
865O 4898 ';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($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