How to read a large file line by line?

Question

I want to read a file line by line, but without completely loading it in memory.

My file is too large to open in memory, and if try to do so I always get out of memo

Answer 1

If you're opening a big file, you probably want to use Generators alongside fgets() to avoid loading the whole file into memory:

/**
 * @return Generator
 */
$fileData = function() {
    $file = fopen(__DIR__ . '/file.txt', 'r');

    if (!$file)
        die('file does not exist or cannot be opened');

    while (($line = fgets($file)) !== false) {
        yield $line;
    }

    fclose($file);
};

Use it like this:

foreach ($fileData() as $line) {
    // $line contains current line
}

This way you can process individual file lines inside the foreach().

Note: Generators require >= PHP 5.5