Data transform "page_history" column of a CSV file

index.php

<?php

/**
 * @author Laurent Constantin
 * Alter the 'page_history' column of a CSV file with emotions.
 * A map between page number and emotion's name is required in a csv format.
 */
class WhatDoYouDo4Love
{
    /**
     * Reads a CSV and return it as an array
     *
     * @param string $filename
     *
     * @param string $separator
     *
     * @return mixed[][] csv content
     */
    protected static function getCsvContent($filename, $separator = ",")
    {
        $result = [];
        if (($handle = fopen($filename, "r")) !== false) {
            while (($data = fgetcsv($handle, null, $separator)) !== false) {
                $result[] = $data;
            }
            fclose($handle);
        } else {
            throw new \RuntimeException("Cannot open file $filename");
        }

        return $result;
    }

    /**
     * Remove all empty lines from array
     *
     * @param array $data
     *
     * @return array
     */
    protected static function clearEmptyLines(array $data)
    {
        return array_filter(
            $data,
            function ($el) {
                if (is_array($el)) {
                    $el = self::clearEmptyLines($el);
                }

                return false === empty($el);
            }
        );
    }

    /**
     * Read the codeBook that is used to replace values.
     * Ex:
     * > Happy1,5367060
     * > Neutral1,5367075
     * > Tendress1,5367064
     *  Will be an array [5367060 => Happy1, 5367075 => Neutral1, etc..]
     *
     * @param $codeBookFile
     *
     * @return array Emotion indexed by code
     */
    public static function createCodeBookMap($codeBookFile)
    {
        $data = self::getCsvContent($codeBookFile);
        $data = self::clearEmptyLines($data);
        $map  = [];
        foreach ($data as $line) {
            $map[$line[1]] = $line[0];
        }

        return $map;
    }

    /**
     * Transform the column
     *
     * @param string $dataFile         Filename for data
     * @param string $codeBookFile     Filename for codeBook
     * @param string $columnName       Column name to replace for the page history
     * @param string $historySeparator Separator to use inside the page history
     *
     * @return mixed[][]
     */
    public static function replacePageHistory(
        $dataFile,
        $codeBookFile,
        $columnName = "page_history",
        $historySeparator = ","
    ) {


        $data = self::getCsvContent($dataFile);

        // Avoid empty file
        if (empty($data)) {
            throw new \RuntimeException("$dataFile is empty");
        }

        // Search column 'page_history' in headers
        $headers = array_shift($data);
        $index   = array_search($columnName, $headers);
        if (false === $index) {
            throw new \RuntimeException("Header $columnName not found");
        }

        // Replace them with value in the map
        $map = self::createCodeBookMap($codeBookFile);
        foreach ($data as $key => $line) {
            // get the page history value
            $pageHistory = explode($historySeparator, $data[$key][$index]);
            // Remove unknown values
            $pageHistory = array_filter(
                $pageHistory,
                function ($el) use ($map) {
                    return isset($map[$el]);
                }
            );
            // Replace values with emotions
            $pageHistory = array_map(
                function ($el) use ($map) {
                    return isset($map[$el]) ? $map[$el] : $el;
                }
                ,
                $pageHistory
            );
            // Put it back into data
            $data[$key][$index] = implode($historySeparator, $pageHistory);
        }

        // Re-add header
        array_unshift($data, $headers);

        return $data;
    }

    /**
     * Create a new CSV file
     * @param string $fileName
     * @param array $data
     */
    public static function buildCsvFile($fileName, array $data)
    {
        $output = fopen($fileName, 'w');
        if (false === $output) {
            throw new \RuntimeException("Cannot open $fileName for writing");
        }

        foreach ($data as $line) {
            fputcsv($output, $line);
        }
        fclose($output);
    }


}

error_reporting(E_ALL);

$dataFile = "data_project_797147_2017_05_06.csv";
$data     = WhatDoYouDo4Love::replacePageHistory($dataFile, "codebook_project_797147_2017_05_05.csv");

$output   = sprintf("%s-%s.csv", time(), $dataFile);
WhatDoYouDo4Love::buildCsvFile($output, $data);
printf("File created as '%s'\n", $output);