StreamingJsonWriter.php

<?php

/**
 * Streaming json writer. Call generator to set up,
 * file isn't opened until you call send().
 * 
 * Pass objects with send until you're done. You can call send(null) to close
 * or let the finally finish up and close out the file at end of execution.
 * 
 * @param string $file - File path to write to
 * @param bool $pretty - Pretty print on or off
 * @param string $mode - fopen mode, in case you want to append
 * 
 * Usage is simple:
 * <code>
 * $js = streamToJson('test.json', true);
 * $js->send(['a' => 42]);
 * $js->send(['b' => 33, 'c' => 5]);
 * $js->send(null);
 * </code>
 */
function streamToJson($file, $pretty = false, $mode = 'w')
{
    $first = true;
    $fp = fopen($file, $mode);
    fputs($fp, "[\n");
    try {
        while(($obj = yield) !== null) {
            $json = json_encode($obj, (($pretty)?JSON_PRETTY_PRINT:0));
            if($first === false)
                fputs($fp, ",\n");
            fputs($fp, "$json");
            $first = false;
        }
     } finally {
         fputs($fp, "\n]");
         fclose($fp);
     }
}