Parse RDF/XML to RDF/PHP using the rapper command line tool

rapper_parse.php

<?php

$URL = 'http://dbpedia.org/resource/London.rdf';
$DATA = file_get_contents('london.rdf');
$FORMAT = "rdfxml";


$start = microtime(true);

// Open a pipe to the rapper command
$descriptorspec = array(
    0 => array("pipe", "r"),
    1 => array("pipe", "w"),
    2 => array("pipe", "w")
);

$process = proc_open(
    escapeshellcmd('rapper').
    " --quiet ".
    " --input " . escapeshellarg($FORMAT).
    " --output json ".
    " --ignore-errors ".
    " --input-uri " . escapeshellarg($URL).
    " --output-uri -".
    " - ",
    $descriptorspec, $pipes, '/tmp', null
);
if (is_resource($process)) {
    // $pipes now looks like this:
    // 0 => writeable handle connected to child stdin
    // 1 => readable handle connected to child stdout
    // 2 => readable handle connected to child stderr

    fwrite($pipes[0], $DATA);
    fclose($pipes[0]);

    $json = stream_get_contents($pipes[1]);
    fclose($pipes[1]);
    $rdfphp = json_decode($json);
    $error = stream_get_contents($pipes[2]);
    fclose($pipes[2]);

    // It is important that you close any pipes before calling
    // proc_close in order to avoid a deadlock
    $returnValue = proc_close($process);
    if ($returnValue) {
        throw new EasyRdf_Exception(
            "Failed to parse RDF ($returnValue): ".$error
        );
    }
} else {
    throw new EasyRdf_Exception(
        "Failed to execute rapper command."
    );
}


$duration = microtime(true) - $start;
print "  Parse time: $duration seconds\n";