CODEWITHSUNDEEP
phptext-filessplfileobject
reddy
reddy

Reputation: 1821

PHP reading next line in text file while using lazy loading?

I have a text file that I want to read line by line. For each line I also need the value from the next line, so I need something to read the next line while in the current line.

I have read through many answers here that I can do this with a foreach loop, but it requires reading the whole file in ahead. I am looking for something to only read as needed.

Here is what I got so far with SplFileObject.

$file = new \SplFileObject($textFile);
$lastNumber = 500;

while (!$file->eof()) {
    $currentLine = $file->fgets();

    $currentNumber = intval($currentLine);
    $file->next();

        if ($file->eof()) {
            $nextNumber = intval($lastNumber);
        } else {
            $nextNumber = intval($file->fgets()) - 1;
        }

        echo $currentNumber . ', ' . $nextNumber . '<br>';

}

Suppose I have a text that have lines like this

0
100
200
300
400

I want them to print out like this

0, 99
100, 199
200, 299
300, 399
400, 500

But my code was skipping every other line

0, 99
200, 299
400, 500

My guess is that my while loop and the $file->next() each moves the line by 1 every loop, that's why the skip. But without the next() call, I don't know how to get the value of the next line. How do I fix this?

Upvotes: 0

Views: 251

Answers (1)

Tunji Oyeniran
Tunji Oyeniran

Reputation: 4394

Use this PHP Code Solution.

  $textFile = 'text.txt';

  $file = new SplFileObject($textFile);
  $lastNumber = 500;

  foreach ($file as $lineNumber => $line) {
    $currentNumber = intval($file->current());

    if ($lineNumber === 0) {
      $previousNumber = $currentNumber;
      continue;
    } else {
      $nextNumber = $currentNumber - 1;
      echo $previousNumber . ', ' . $nextNumber . '<br>';

      $previousNumber = $currentNumber;

      if ($file->eof()) {
        $nextNumber = intval($lastNumber);
        echo $currentNumber . ', ' . $nextNumber . '<br>';
      }
    }
  }

Upvotes: -1

Related Questions