1.13.1. ProblemYou need to break apart fixed-width records in strings. 1.13.2. SolutionUse substr( ) as shown in Example 1-34. Parsing fixed-width records with substr( )
Or unpack( ) , as shown in Example 1-35. Parsing fixed-width records with unpack( )
1.13.3. DiscussionData in which each field is allotted a fixed number of characters per line may look like this list of books, titles, and publication dates: <?php $booklist=<<<END Elmer Gantry Sinclair Lewis1927 The Scarlatti InheritanceRobert Ludlum 1971 The Parsifal Mosaic Robert Ludlum 1982 Sophie's Choice William Styron1979 END; ?> In each line, the title occupies the first 25 characters, the author's name the next 14 characters, and the publication year the next 4 characters. Knowing those field widths, you can easily use substr( ) to parse the fields into an array: <?php $books = explode("\n",$booklist); for($i = 0, $j = count($books); $i < $j; $i++) { $book_array[$i]['title'] = substr($books[$i],0,25); $book_array[$i]['author'] = substr($books[$i],25,14); $book_array[$i]['publication_year'] = substr($books[$i],39,4); } ?> Exploding $booklist into an array of lines makes the looping code the same whether it's operating over a string or a series of lines read in from a file. The loop can be made more flexible by specifying the field names and widths in a separate array that can be passed to a parsing function, as shown in the pc_fixed_width_substr( ) function in Example 1-36. pc_fixed_width_substr( )
The variable $line_pos keeps track of the start of each field and is advanced by the previous field's width as the code moves through each line. Use rtrim( ) to remove trailing whitespace from each field. You can use unpack( ) as a substitute for substr( ) to extract fields. Instead of specifying the field names and widths as an associative array, create a format string for unpack( ). A fixed-width field extractor using unpack( ) looks like the pc_fixed_width_unpack( ) function shown in Example 1-37. pc_fixed_width_unpack( )
Because the A format to unpack( ) means "space-padded string," there's no need to rtrim( ) off the trailing spaces. Once the fields have been parsed into $book_array by either function, the data can be printed as an HTML table, for example: <?php $book_array = pc_fixed_width_unpack('A25title/A14author/A4publication_year', $books); print "<table>\n"; // print a header row print '<tr><td>'; print join('</td><td>',array_keys($book_array[0])); print "</td></tr>\n"; // print each data row foreach ($book_array as $row) { print '<tr><td>'; print join('</td><td>',array_values($row)); print "</td></tr>\n"; } print '</table>\n'; ?> Joining data on </td><td> produces a table row that is missing its first <td> and last </td>. We produce a complete table row by printing out <tr><td> before the joined data and </td></tr> after the joined data. Both substr( ) and unpack( ) have equivalent capabilities when the fixed-width fields are strings, but unpack( ) is the better solution when the elements of the fields aren't just strings. If all of your fields are the same size, str_split( ) is a handy shortcut for chopping up incoming data. Available in PHP 5, it returns an array made up of sections of a string. Example 1-38 uses str_split( ) to break apart a string into 32-byte pieces. Chopping up a string with str_split( )
1.13.4. See AlsoFor more information about unpack( ), see Recipe 1.16 and http://www.php.net/unpack; documentation on str_split( ) at http://www.php.net/str_split; Recipe 4.8 discusses join( ) . |