A function that returns an array containing raw MNIST images

loadMNISTImages.php

<?php

    public function loadMNISTImages($filename)
    {
        $fp = fopen($filename, 'rb');

        $array = unpack("N4", fread($fp, 16));
        $magic = $array[1];

        if($magic != 2051) {
            throw new Exception("Bad magic number in $filename", 1);
        }

        $numOfImages  = $array[2];
        $numOfRows    = $array[3];
        $numOfColumns = $array[4];

        $pixelsPerImage = $numOfRows * $numOfColumns;

        $images = [];

        while ( $stream = fread($fp, $pixelsPerImage) ) {
            $image = unpack("C{$pixelsPerImage}", $stream);
            $images[] = implode(',', $image);
        }

        fclose($fp);

        return $images;
    }