Iterating File Contents with SPL

I noticed a lot of people are still using the classic filepointer approach to read a file line by line:

$handle = fopen ("file.txt", "r");
while (!feof($handle)) {
    $buffer = fgets($handle);
    echo $buffer;
}
fclose ($handle);

While there is nothing wrong with doing things the old school way, PHP also offers SplFileObject for quite some time now:

$file = new SplFileObject("file.txt");
while (!$file->eof()) {
  echo $file->fgets();
}

Not only does this shorten your code by two lines, but it also let’s you work with an Object instead of a Resource now. Almost all of the procedural functions available for file handling are also available as methods of SplFileObject.

If that’s not enough reason to switch already, SplFileObject also implements the Iterator interface, which means you can shorten the above code to a simple foreach loop:

foreach (new SplFileObject("file.txt") as $lineNumber => $content) {
    printf("Line %d: %s", $lineNumber, $content);
}

There is more. Because SplFileObject also implements SeekableIterator you can easily jump to specific lines without having to count lines via some temp variable in your loop. How much more convenient can it get?

$file = new SplFileObject("file.txt");
$file->seek(9);        // zero-based, so it's line 10
echo $file->current(); // outputs line 10

And of course you can stack an SplFileObject into other Iterators, for instance the LimitIterator to limit how many lines should be iterated over:

$linesTenToTwentyIterator = new LimitIterator(
    new SplFileObject("file.txt"),
    9, // start at line 10
    10 // iterate 10 lines
);
foreach ($linesTenToTwentyIterator as $line) {
    echo $line; // outputs line 10 to 20
}

SplFileObject is complemented by SplTempFileObject and SplFileInfo. The first offers an object oriented interface for a temporary file, including in-memory files. As such it is similar to file pointers opened with php://temp or php://memory as file descriptors.

SplFileInfo offers a high-level object oriented interface to information for an individual file. This includes methods for getting the realpath, basename and so on. SplFileInfo is actually the parent class of the other two.

So next time you’re going to whip out another file pointer, remember there is a nice OO alternative.

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Published

16 May 2011

Iterating File Contents with SPL

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