{"id":2211,"date":"2014-04-17T16:19:43","date_gmt":"2014-04-17T14:19:43","guid":{"rendered":"http:\/\/www.nyamsprod.com\/blog\/?p=2211"},"modified":"2014-04-29T21:54:05","modified_gmt":"2014-04-29T19:54:05","slug":"stream-filtering-with-splfileobject","status":"publish","type":"post","link":"https:\/\/nyamsprod.com\/blog\/stream-filtering-with-splfileobject\/","title":{"rendered":"Stream Filtering with SplFileObject"},"content":{"rendered":"
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Attention:<\/strong> Les informations de ce billet sont susceptibles d'être obsolètes car vieux de plus 2 ans.<\/p>\n

Warning: <\/strong> The information you are reading may be obsolete, this post was published more than 2 years ago.<\/p>\n<\/div>

Since PHP4 days, the language has been able to interact with streams<\/a>, a resource object that can be read from or written to in a linear fashion. This feature can help us applying filters function on streams while reading from or written to them. This can be interesting if you want, for instance, to compress or decompress, on the fly, a file before or after accessing it.
\nTo apply those filters, the developer must use PHP stream filtering functions stream_filter_*<\/code> and\/or the php meta wrapper php:\/\/filter<\/code> and have access to a PHP file resource. For instance, any resource returned by fopen<\/code> can be filtered using PHP.<\/p>\n

$path = 'path\/to\/my\/file.txt';\r\n$fp = fopen($path, 'r');\r\n$filter1 = stream_filter_append($fp, 'string.toupper');\r\n$filter2 = stream_filter_prepend($fp, 'string.rot13', STREAM_FILTER_READ);\r\n$res = fgets($fp); \/\/the output text is ROT13 and then uppercased\r\nstream_filter_remove($filter2);\r\nrewind($fp);\r\n$res = fgets($fp); \/\/the output text is only uppercased<\/code><\/pre>\n
The stream filters can be applied when reading,\u00a0 writing or on both actions. They can be removed at any given time. This feature is truly powerful.<\/p>\n
Now let’s jump to today’s post-PHP 5.3+ world where objects like SplFileObject<\/code> where created to offer an OOP approach to file interaction. With the added benefit of using Iterator<\/code> and many other goodies, being able to apply PHP stream filtering features on a SplFileObject<\/code> as easily as on a file resource would be great but that is not currently possible. The main reason being that the SplFileObject<\/code> class does not expose it’s internal file pointer resource, so using any stream_filter_*<\/code> is simply not possible<\/del> adding stream filters to an instantiate SplFileObject<\/code> object is not possible.<\/p>\n
If you want to apply stream filters to a SplFileObject<\/code> object, you are required to instantiate the object using the meta wrapper php:\/\/filter<\/code>.<\/p>\n
$path = 'path\/to\/my\/file.txt';\r\n$file = new SplFileObject('php:\/\/filter\/read=string.rot13|string.toupper\/resource='.$path, 'r');\r\n$file->fgets();  \/\/the output text is ROT13 and then uppercased<\/code><\/pre>\n
This technique works but has several limitations, here are two that come directly in mind:<\/p>\n