Set referer for getting referring page title to nothing, then avoid fetching empty referers

includes/pixel.php

@@ -1,63 +1,83 @@
 <?php
+/**
+ * Tracking mechanism for the tracking pixel.
+ */
 
-// function to get the title of the referring url
+
+/**
+ * Given a URL, try to get the <title>.
+ *
+ * @param String $url The URL to find a <title></title>.
+ * @return void|String The contents of <title></title>.
+ */
 function wprtt_get_referring_page_title( $url ) {
 
-	$response = wp_remote_get( $url );
+	$args = array(
+		'redirection' => 1,
+		'headers' => array(
+			'Referer' => '',
+		),
+	);
+
+	$response = wp_remote_get( $url, $args );
 
-	// if there was no issue grabbing the url, continue
+	// if there was no issue grabbing the url, continue.
 	if ( ! is_wp_error( $response ) ) {
 
-		// find the title element inside of the response body
+		// find the title element inside of the response body.
 		$response = preg_match( '/<title.[^>]*>(.*)<\/title>/siU', $response['body'], $title_matches );
 
-		// if a title element was found, let's get the text from it
+		// if a title element was found, let's get the text from it.
 		if ( $title_matches ) {
 
 			// clean up title: remove EOL's and excessive whitespace.
 			$title = preg_replace( '/\s+/', ' ', $title_matches[1] );
 			$title = trim( $title );
 			$title = rawurlencode( $title );
 
-			// return our found title
+			// return our found title.
 			return $title;
 
 			// if there were no title matches found, don't continue
 		} else {
 
+		// if there were no title matches found, don't continue.
+		} else {
 			return;
-
 		}
 	}
-
 }
 
 if ( isset( $_GET['post'] ) ) {
 
-	// set up all of our post vars we want to track
+	// set up all of our post vars we want to track.
 	$shared_post_id = absint( $_GET['post'] );
 	$shared_post    = get_post( $shared_post_id );
 
 	$shared_post_slug      = rawurlencode( $shared_post->post_name );
 	$shared_post_permalink = get_permalink( $shared_post_id );
+
+	$url       = '';
+	$url_title = '';
+	$url_host  = '';
 
 	if ( array_key_exists( 'HTTP_REFERER', $_SERVER ) ) {
 
 		if ( isset( $_SERVER['HTTP_REFERER'] ) ) {
 			$url = esc_url_raw( $_SERVER['HTTP_REFERER'] );
 		}
 
-		$url_title = wprtt_get_referring_page_title( $url );
-		$url_title = str_replace( ' ', '%20', $url_title );
-
-		$url_host = parse_url( $url, PHP_URL_HOST );
-		$url_path = parse_url( $url, PHP_URL_PATH );
+	if ( ! empty( $_SERVER['HTTP_REFERER'] ) ) {
+		$url = esc_url_raw( wp_unslash( $_SERVER['HTTP_REFERER'] ) );
+	}
 
-	} else {
+	if ( ! empty( $url ) ) {
+		$url_host = wp_parse_url( $url, PHP_URL_HOST );
+		$url_path = wp_parse_url( $url, PHP_URL_PATH );
 
-		$url       = '';
-		$url_title = '';
-		$url_host  = '';
+		// Try to get the page title.
+		$url_title = wprtt_get_referring_page_title( $url );
+		$url_title = str_replace( ' ', '%20', $url_title );
 
 	}
 
@@ -66,18 +86,56 @@ function wprtt_get_referring_page_title( $url ) {
 		exit;
 	}
 
-	$value = get_post_meta( $shared_post_id, 'republication_tracker_tool_sharing', true );
-	if ( $value ) {
-		if ( isset( $value[ $url ] ) ) {
-			$value[ $url ]++;
+	// Avoid tracking hits that have no site to track.
+	if ( ! empty( $url ) && ! empty( $url_host ) ) {
+
+		$value = get_post_meta( $shared_post_id, 'republication_tracker_tool_sharing', true );
+		if ( $value ) {
+			if ( isset( $value[ $url ] ) ) {
+				$value[ $url ]++;
+			} else {
+				$value[ $url ] = 1;
+			}
 		} else {
-			$value[ $url ] = 1;
+			$value = array(
+				$url => 1,
+			);
+		}
+		$update = update_post_meta( $shared_post_id, 'republication_tracker_tool_sharing', $value );
+
+		// if our google analytics tag is set, let's push data to it.
+
+		if ( isset( $_GET['ga'] ) && ! empty( $_GET['ga'] ) ) {
+
+			// our base url to ping GA at.
+			$analytics_ping_url = "https://www.google-analytics.com/collect?v=1";
+
+			// create all of our necessary params to track
+			// the docs for these params can be found at: https://developers.google.com/analytics/devguides/collection/analyticsjs/events
+			$analytics_ping_params = array(
+				'tid' => sanitize_text_field( wp_unslash( $_GET['ga'] ) ),
+				'cid' => '555',
+				't' => 'pageview',
+				'dl' => $shared_post_permalink,
+				'dh' => $url_host,
+				'dp' => $shared_post_slug,
+				'dr' => $url,
+				'dt' => $url_title,
+				'an' => 'Republication',
+				'aid' => $url_host,
+				'av' => 'Republication Tracker v1',
+			);
+
+			// create query based on our params array.
+			$analytics_ping_params = http_build_query( $analytics_ping_params );
+
+			$response = wp_remote_post( $analytics_ping_url . '&' . $analytics_ping_params );
 		}
 	} else {
 		$value = array(
 			$url => 1,
 		);
-	}
+  }
 	$update = update_post_meta( $shared_post_id, 'republication_tracker_tool_sharing', $value );
 
 	// if our google analytics tag is set, let's push data to it