PHP parse GeoPackage

ParseGeoPackage.php

<?php

/**
 * Parse GeoPackageBinaryHeader
 * 
 * References
 * 
 * http://www.geopackage.org/spec/#gpb_spec
 * 
 * https://en.wikipedia.org/wiki/Well-known_text
 * http://php.net/manual/en/function.unpack.php
 * http://ngageoint.github.io/geopackage-js/ (NodeJS + SQL.js Demo)
 * 
 * @param string $filename
 */
protected function parseGeoPackageGeometry($filename)
{
    // Default values
    $header = [
        'magic'     => '',
        'version'   => 0,
        'flags'     => 0,
        'srs_id'    => 0,
        'envelope'  => []
    ];
    $wkb = '';
    
    // Open binary
    $h = fopen($filename, 'rb');
    if (!$h) {
        throw new \Exception('Could not open stream (geometry data)');
    }
        
    // Get stream stats
    $fstat = fstat($h);
    $total = $fstat['size'];
    $read = 0;

    // Parse header
    $bytes = unpack('A2magic/c1version/c1flags', fread($h, 4));
    $read += 4;
    $header['magic'] = $bytes['magic'];
    $header['version'] = $bytes['version'];
    $header['flags'] = $bytes['flags'];
    $header['envelop_flag'] = ($header['flags'] >> 1) & 7;
    $header['byte_order'] = $header['flags'] & 1;

    // Parse SRID
    $unpack_op = $header['byte_order'] ? 'V' : 'N';
    $bytes = array_values(unpack($unpack_op, fread($h, 4)));
    $read += 4;
    $header['srs_id'] = $bytes[0];

    switch ($header['envelop_flag']) {
    case 1: // 32 bytes envelop
        $unpack_op = $header['byte_order'] ? 'f*' : 'f*';
        $bytes = array_values(unpack('f*', fread($h, 32)));
        $header['envelope'] = [
            'minx' => $bytes[0],
            'miny' => $bytes[1],
            'maxx' => $bytes[2],
            'maxy' => $bytes[3],
            'minz' => false,
            'maxz' => false,
            'minm' => false,
            'maxm' => false
        ];
        $read += 32;
        break;
    case 2: // 48 bytes envelop
        $unpack_op = $header['byte_order'] ? 'f*' : 'f*';
        $bytes = array_values(unpack('f*', fread($h, 48)));
        $header['envelope'] = [
            'minx' => $bytes[0],
            'miny' => $bytes[1],
            'maxx' => $bytes[2],
            'maxy' => $bytes[3],
            'minz' => $bytes[4],
            'maxz' => $bytes[5],
            'minm' => false,
            'maxm' => false
        ];
        $read += 48;
        break;
    case 3: // 48 bytes envelop
        $unpack_op = $header['byte_order'] ? 'f*' : 'f*';
        $bytes = array_values(unpack('f*', fread($h, 48)));
        $header['envelope'] = [
            'minx' => $bytes[0],
            'miny' => $bytes[1],
            'maxx' => $bytes[2],
            'maxy' => $bytes[3],
            'minz' => false,
            'maxz' => false,
            'minm' => $bytes[4],
            'maxm' => $bytes[5]
        ];
        $read += 48;
        break;
    default: ;// 0 envelop
    }

    // Get WKB from bytes left
    $wkb = fread($h, $total - $read);

    // Close handler
    fclose($h);
    
    return [$header, $wkb];
}

Appears you are reading floats for minx miny etc, but all of those are doubles (8 bytes).

For reference, here's our implementations in various languages:
https://github.com/ngageoint/geopackage-js/blob/master/lib/geom/geometryData.js
https://github.com/ngageoint/geopackage-ios/blob/master/geopackage-ios/geom/GPKGGeometryData.m
https://github.com/ngageoint/geopackage-core-java/blob/master/src/main/java/mil/nga/geopackage/geom/GeoPackageGeometryData.java

This is great, parsing the geod blobs nicely from the https://gadm.org/ data. Thank you.

The only change I needed to make was to replace $filename with $filestream, leaving it up to the caller to option the stream. In my case the stream is created from a string that is selected directly from the GeoPackage SQLite tables. No files are involved.