Generate Waveform from music file with PHP

classAudioFileModified.php

<?php
//Refer : https://github.com/ashishmaurya/waveform-using-php/blob/master/classAudioFileModified.php
//For full class file
function getVisualizationSVG($output) {
        $width = $this->visual_width;
        $height = $this->visual_height;
        $height_channel = $height / $this->wave_channels;
        if ($this->wave_filename <> "" && $this->wave_id == "RIFF" && $this->wave_type == "WAVE" && ($this->wave_channels >= 1 && $this->wave_channels <= 2) && $this->wave_bits % 8 == 0) {
            $file = fopen($this->wave_filename, "r");

            // read the first 12 bytes (RIFF- & WAVE-chunk)

            for ($i = 0; $i < 12; $i++) {
                $null = fgetc($file);
            }

            // Read the next chunk-id, supposed to be "fmt "

            $chunk_id_3 = fgetc($file) . fgetc($file) . fgetc($file) . fgetc($file);
            if ($chunk_id_3 == "fmt ") {
                $chunk_size_3 = $this->longCalc(fgetc($file), fgetc($file), fgetc($file), fgetc($file), 0);
                for ($i = 0; $i < $chunk_size_3; $i++) {
                    $null = fgetc($file);
                }

                // Read the next chunk-id, supposed to be "data"				
                $chunk_id_4 = "";
                while ($chunk_id_4 <> "data" && !feof($file)) {
                    $chunk_id_4 = fgetc($file) . fgetc($file) . fgetc($file) . fgetc($file);
                    if ($chunk_id_4 <> "data") {
                        $chunk_size_4 = $this->longCalc(fgetc($file), fgetc($file), fgetc($file), fgetc($file), 0);
                        for ($i = 0; $i < $chunk_size_4; $i++) {
                            $null = fgetc($file);
                        }
                    }
                }
                if ($chunk_id_4 == "data") {
                    $chunk_size_4 = $this->longCalc(fgetc($file), fgetc($file), fgetc($file), fgetc($file), 0);
                    $visualData = array();
                    $bytes_per_frame = ($this->wave_bits / 8) * ($this->wave_channels);
                    $bytes_per_channel = ($this->wave_bits / 8);
                    $frames = $chunk_size_4 / $bytes_per_frame;
                    $visual_frames = ceil($frames / $width);
                    $frame_index = 1;
                    $data_index = 1;

                    // revised code -- computing bytes per pixel allows quick processing of large (>10MB) wavs by fseek()ing past unused data
                    $bytes_per_pixel = floor($chunk_size_4 / $width);
                    $currentindex = 0;
                    while (!feof($file) && $currentindex < $chunk_size_4) {
                        $loopindex = 0;
                        for ($j = 0; $j < $this->wave_channels; $j++) {
                            $bytes = array();
                            for ($i = 0; $i < $bytes_per_channel; $i++) {
                                $bytes[$i] = fgetc($file);
                                $loopindex++;
                            }
                            switch ($bytes_per_channel) {
                                case 1: $visualData[$j][$data_index] = $this->shortCalc($bytes[0], $bytes[1], 0);
                                    break;
                                case 2: $f = 128;
                                    if (ord($bytes[1]) & 128)
                                        $f = 0;
                                    $x = chr((ord($bytes[1]) & 127) + $f);
                                    $visualData[$j][$data_index] = floor($this->shortCalc($bytes[0], $x, 0) / 256);
                                    break;
                            }
                            if (($j + 1) == $this->wave_channels) {
                                $data_index++;
                            }
                        }
                        $currentindex+= ( $bytes_per_pixel - $loopindex );
                        fseek($file, $bytes_per_pixel, SEEK_CUR);
                    }



                    // this for-loop draws a graph for every channel
                    for ($j = 0; $j < 1; $j++) {
                        $last_x = 1;
                        $last_y = $height_channel / 2;

                        // this for-loop draws the graphs itself
                        $data = array();
                        for ($i = 1; $i < sizeof($visualData[$j]); $i++) {
                            $faktor = 128 / ($height_channel / 2);
                            $val = $visualData[$j][$i] / $faktor;
                            $data[] = $val;
                        }

                        $this->data = $data;

                        //Genrate Wave SVG file
                        $f = fopen($output, "w");
                        $data = $this->data;

                        $txt = '<svg xmlns="http://www.w3.org/2000/svg" width="' . $this->visual_width . '" height="' . $this->visual_height . '">';
                        $txt .= "<style>";
                        $txt .= "line{stroke:#CCC;stroke-width:1.5}";
                        $txt .= "</style>";
                        $COUNT_POINT = count($data);
                        $MAX_NUMBER_OF_POINT = 180;
                        $SKIP_COUNT = floor($COUNT_POINT / $MAX_NUMBER_OF_POINT);

                        for ($i = 0; $i < $COUNT_POINT; $i++) {

                            if ($i % $SKIP_COUNT != ($SKIP_COUNT - 1)) {
                                continue;
                            }
                            $y1_4 = $this->visual_height / 4;
                            $y1 = $this->visual_height - $y1_4;
                            $y2 = $data[$i];
                            $y2_4 = ($this->visual_height - $y2) / 4;
                            $y2 = $y2 - $y2_4;


                            $y1_4 = $y1 + 1;
                            $y2_4 +=$y1_4;

                            $y2 = number_format((float) $y2, 1, '.', '');
                            $y2_4 = number_format((float) $y2_4, 1, '.', '');
                            $y2 = round($y2);
                            $y2_4 = round($y2_4);
                            $txt .= '<line x1="' . $i . '" y1="' . $y2 . '" x2="' . $i . '" y2="' . $y2_4 . '"/>';
                        }
                        $txt .= '<line x1="' . 0 . '" y1="' . $y1_4 . '" x2="' . $this->visual_width . '" y2="' . $y1_4 . '" style="stroke:#FFF;stroke-width:1;"/>';
                        $txt.="</svg>";
                        fwrite($f, $txt);
                        fclose($f);
                    }
                }
            }
            fclose($file);
        } else {
            // AudioSample - AudioFile-Object not initialized!
        }
}