Optimised CSV file reading with PJP

optimised_file_read.php

<?php

Class CSVHandle 
{  
    const CHUNK_SIZE  = 4096;
    private $chunk = [];
    private $buffer = '';
    private $fp = null; 

    /**
     * Opens a file pointer and attaches this to the object
     * @param string $filename 
     * @param string $modifier 
    **/
    public function open(string $filename, string $modifier)
    {
        $this->fp = fopen($filename, $modifier);
    } 

    /**
     * Closes a file pointer attached to an object
    **/
    public function close() 
    { 
        if ($this->fp !== null) {
          fclose($this->fp);
        }
    } 

    /**
     * Returns the next line from a CSV file, either from the 
     * latest chunk in memory, or by setting up the next chunk
     *
     * @return array
    **/
    public function getLine() : array
    {
        if (empty($this->chunk)) { 
            if (feof($this->fp) {
                return false;
            }
            // if we're empty get the next chunk using the previous buffer
            $this->chunk = $this->buffer . fread(
                $this->fp, 
                self::CHUNK_SIZE
            ); 
            // explode the chunk into lines
            $this->chunk = preg_split("/\\r\\n|\\r|\\n/", $this->chunk); 
            // if this isn't the end of the file
            if (!feof($this->fp)) {
                // buffer out the last line
                $this->buffer = array_pop($this->chunk);
            }
        } 
        // return the next line off the beginning of the stack
        return (
          "" === ($line = array_shift($this->chunk))
        ) ? false : str_getcsv($line);
  }

  /**
   * Writes a line to a file pointer
  **/    
  public function writeLine($values)
  {
      return fputcsv($this->fp, $values, ',', '\"');
  }
}