php json保存并读取多个数组到文件

Question

I am trying to save multiple php arrays one at a time. The arrays come to me from a parser function also one at a time. I used to keep them all in memory and then write them all at once like this:

while($onearr = parser())
     $allarr[] = $onearr;

  ..
  ..
  fwrite($filename,json_encode($allarr));

But this logic did not hold for long. I started running out of memory quickly. I want to write the arrays one at a time to the same file and read them one at a time too. This is my writer function:

function savearr($onearr) {        
    if($fp = fopen('arrFile.json','a+'))  {    
       $rc = fwrite($fp, json_encode($onearr));
       fclose($fp);
    }   
}

Now I cannot figure a way to read these arrays! Any way to do it? I tried reading the whole file at once but was not sure how to parse it correctly into individual arrays to match the original!

Thanks in advance

Answer 1

Firstly, you may want to rethink your savearr() function, you're opening/closing the file each time you write the array. Perhaps a class note: none of this was tested:

class ArrayWriter {
  protected $fp;
  public function __construct() {
    $this->fp = fopen('arrFile.json', 'a+');
    if(!$this->fp) die("Unable to open file");
  }

  public function __destruct() {
    if($this->fp) fclose($this->fp);
  }

  public function write($array = array()) {
    if($this->fp) fwrite($this->fp, json_encode($array) . "
");
  }
}

Now that we've cleared that up, we can do the reverse to read:

function read() {
  $arrays = file('arrFile.json');
  $result = array();
  foreach($arrays as $line)
    $result[] = json_decode($line);
  }
  return $result;
}