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Processing Large Files Using PHP

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Processing Large Files Using PHP

In this quick tutorial, you'll learn how to process large files in PHP, avoiding methods that won't work because of memory limitations.

· Web Dev Zone ·
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If you want to process large files using PHP, you may use some of the ordinary PHP functions like file_get_contents() or file() which have a limitation when working with very large files.

Memory Limitation

These functions rely on the memory_limit setting in the php.ini file; you may increase the value but these functions still are not suitable for very large files because these functions will put the entire file contents into memory at one point.

Any file that has a size larger than the memory_limit setting will not be loaded into memory, so what if you have 20 GB file and you want to process it using PHP?

Bad User Experience

Another limitation is the speed of producing output. Let's assume that you will accumulate the output in an array then output it at once which gives a bad user experience.

For this limitation, we can use the yield keyword to generate an immediate result.

SplFileObject Class

In this post, we will use the SplFileObject class which is a part of Standard PHP Library.

For our demonstration, I will create a class to process large files using PHP.

The class will take the file name as input to the constructor:

class BigFile
{
    protected $file;
 
    public function __construct($filename, $mode = "r")
    {
        if (!file_exists($filename)) {
 
            throw new Exception("File not found");
        }
 
        $this->file = new SplFileObject($filename, $mode);
    }
 
}

Now we will define a method for iterating through the file, this method will use fgets() function to read one line at a time.

You can create another method that uses the fread() function.

Read Text Files

The fgets() is suitable for parsing text files that include line feeds while fread() is suitable for parsing binary files.

This function will be used to iterate through lines of text files.

protected function iterateText()
{
    $count = 0;
 
    while (!$this->file->eof()) {
 
        yield $this->file->fgets();
 
        $count++;
    }
    return $count;
}


Read Binary Files

Another function which will be used for parsing binary files:

protected function iterateBinary($bytes)
{
    $count = 0;
 
    while (!$this->file->eof()) {
 
        yield $this->file->fread($bytes);
 
        $count++;
    }
}


Read in One Direction

Now we will define a method that will take the iteration type and return NoRewindIterator instance.

We use the NoRewindIterator to enforce reading in one direction.

public function iterate($type = "Text", $bytes = NULL)
{
    if ($type == "Text") {
 
        return new NoRewindIterator($this->iterateText());
 
    } else {
 
        return new NoRewindIterator($this->iterateBinary($bytes));
    }
 
}

Now the entire class will look like this:

class BigFile
{
    protected $file;
 
    public function __construct($filename, $mode = "r")
    {
        if (!file_exists($filename)) {
 
            throw new Exception("File not found");
 
        }
 
        $this->file = new SplFileObject($filename, $mode);
    }
 
    protected function iterateText()
    {
        $count = 0;
 
        while (!$this->file->eof()) {
 
            yield $this->file->fgets();
 
            $count++;
        }
        return $count;
    }
 
    protected function iterateBinary($bytes)
    {
        $count = 0;
 
        while (!$this->file->eof()) {
 
            yield $this->file->fread($bytes);
 
            $count++;
        }
    }
 
    public function iterate($type = "Text", $bytes = NULL)
    {
        if ($type == "Text") {
 
            return new NoRewindIterator($this->iterateText());
 
        } else {
 
            return new NoRewindIterator($this->iterateBinary($bytes));
        }
 
    }
}


Parse Large Files

Let's test our class:

$largefile = new BigFile("file.csv");
 
$iterator = $largefile->iterate("Text"); // Text or Binary based on your file type
 
foreach ($iterator as $line) {
 
    echo $line;
 
}

This class should read any large file without limitations. Great!!

You can use this class in your Laravel projects by autoloading your class and add it to composer.json file.

Now you can parse and process large files using PHP easily.

Keep coming back.

Thank you.

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Topics:
web dev ,php ,tutorial ,memory ,processing

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