PHP Strings Generating Fixed-Width Field Data Records

PHP Strings

Generating Fixed-Width Field Data Records

Problem

You need to format data records such that each field takes up a set amount of characters.

Solution

Example   Generating fixed-width field data records

             $books = array( array('Elmer Gantry', 'Sinclair Lewis', 1927),
                                       array('The Scarlatti Inheritance','Robert Ludlum', 1971),
                                       array('The Parsifal Mosaic','William Styron', 1979) );

             foreach ($books as $book) {
                     print pack('A25A15A4', $book[0], $book[1], $book[2]) . "\n";
             }

Discussion

The format string A25A14A4 tells pack() to transform its subsequent arguments into a 25-character space-padded string, a 14-character space-padded string, and a 4-character space-padded string. For space-padded fields in fixed-width records, pack() provides a concise solution.

To pad fields with something other than a space, however, use substr() to ensure that the field values aren’t too long and str_pad() to ensure that the field values aren’t too short. 

Example   Generating fixed-width field data records without pack( )

             $books = array( array('Elmer Gantry', 'Sinclair Lewis', 1927),
                                       array('The Scarlatti Inheritance','Robert Ludlum', 1971),
                                       array('The Parsifal Mosaic','William Styron', 1979) );

             foreach ($books as $book) {
                    $title = str_pad(substr($book[0], 0, 25), 25, '.');
                    $author = str_pad(substr($book[1], 0, 15), 15, '.');
                    $year = str_pad(substr($book[2], 0, 4), 4, '.');
                    print "$title$author$year\n";
             }