media_handle_upload( string $file_id, int $post_id, array $post_data = array(), array $overrides = array('test_form' => false) )

function media_handle_upload($file_id, $post_id, $post_data = array(), $overrides = array( 'test_form' => false )) {

	$time = current_time('mysql');
	if ( $post = get_post($post_id) ) {
		// The post date doesn't usually matter for pages, so don't backdate this upload.
		if ( 'page' !== $post->post_type && substr( $post->post_date, 0, 4 ) > 0 )
			$time = $post->post_date;
	}

	$file = wp_handle_upload($_FILES[$file_id], $overrides, $time);

	if ( isset($file['error']) )
		return new WP_Error( 'upload_error', $file['error'] );

	$name = $_FILES[$file_id]['name'];
	$ext  = pathinfo( $name, PATHINFO_EXTENSION );
	$name = wp_basename( $name, ".$ext" );

	$url = $file['url'];
	$type = $file['type'];
	$file = $file['file'];
	$title = sanitize_text_field( $name );
	$content = '';
	$excerpt = '';

	if ( preg_match( '#^audio#', $type ) ) {
		$meta = wp_read_audio_metadata( $file );

		if ( ! empty( $meta['title'] ) ) {
			$title = $meta['title'];
		}

		if ( ! empty( $title ) ) {

			if ( ! empty( $meta['album'] ) && ! empty( $meta['artist'] ) ) {
				/* translators: 1: audio track title, 2: album title, 3: artist name */
				$content .= sprintf( __( '"%1$s" from %2$s by %3$s.' ), $title, $meta['album'], $meta['artist'] );
			} elseif ( ! empty( $meta['album'] ) ) {
				/* translators: 1: audio track title, 2: album title */
				$content .= sprintf( __( '"%1$s" from %2$s.' ), $title, $meta['album'] );
			} elseif ( ! empty( $meta['artist'] ) ) {
				/* translators: 1: audio track title, 2: artist name */
				$content .= sprintf( __( '"%1$s" by %2$s.' ), $title, $meta['artist'] );
			} else {
				/* translators: 1: audio track title */
				$content .= sprintf( __( '"%s".' ), $title );
			}

		} elseif ( ! empty( $meta['album'] ) ) {

			if ( ! empty( $meta['artist'] ) ) {
				/* translators: 1: audio album title, 2: artist name */
				$content .= sprintf( __( '%1$s by %2$s.' ), $meta['album'], $meta['artist'] );
			} else {
				$content .= $meta['album'] . '.';
			}

		} elseif ( ! empty( $meta['artist'] ) ) {

			$content .= $meta['artist'] . '.';

		}

		if ( ! empty( $meta['year'] ) ) {
			/* translators: Audio file track information. 1: Year of audio track release */
			$content .= ' ' . sprintf( __( 'Released: %d.' ), $meta['year'] );
		}

		if ( ! empty( $meta['track_number'] ) ) {
			$track_number = explode( '/', $meta['track_number'] );
			if ( isset( $track_number[1] ) ) {
				/* translators: Audio file track information. 1: Audio track number, 2: Total audio tracks */
				$content .= ' ' . sprintf( __( 'Track %1$s of %2$s.' ), number_format_i18n( $track_number[0] ), number_format_i18n( $track_number[1] ) );
			} else {
				/* translators: Audio file track information. 1: Audio track number */
				$content .= ' ' . sprintf( __( 'Track %1$s.' ), number_format_i18n( $track_number[0] ) );
			}
		}

		if ( ! empty( $meta['genre'] ) ) {
			/* translators: Audio file genre information. 1: Audio genre name */
			$content .= ' ' . sprintf( __( 'Genre: %s.' ), $meta['genre'] );
		}

	// Use image exif/iptc data for title and caption defaults if possible.
	} elseif ( 0 === strpos( $type, 'image/' ) && $image_meta = wp_read_image_metadata( $file ) ) {
		if ( trim( $image_meta['title'] ) && ! is_numeric( sanitize_title( $image_meta['title'] ) ) ) {
			$title = $image_meta['title'];
		}

		if ( trim( $image_meta['caption'] ) ) {
			$excerpt = $image_meta['caption'];
		}
	}

	// Construct the attachment array
	$attachment = array_merge( array(
		'post_mime_type' => $type,
		'guid' => $url,
		'post_parent' => $post_id,
		'post_title' => $title,
		'post_content' => $content,
		'post_excerpt' => $excerpt,
	), $post_data );

	// This should never be set as it would then overwrite an existing attachment.
	unset( $attachment['ID'] );

	// Save the data
	$id = wp_insert_attachment( $attachment, $file, $post_id, true );
	if ( !is_wp_error($id) ) {
		wp_update_attachment_metadata( $id, wp_generate_attachment_metadata( $id, $file ) );
	}

	return $id;

}