diff --git a/lib/Core.php b/lib/Core.php
index cef2e4c4..74e5916f 100644
--- a/lib/Core.php
+++ b/lib/Core.php
@@ -38,7 +38,7 @@ set_exception_handler(function($ex){
 	$errorString = "----------------------------------------\n";
 	$errorString .= trim(vds(array_intersect_key($_SERVER, array('REQUEST_URI' => '', 'QUERY_STRING' => '', 'REQUEST_METHOD' => '', 'REDIRECT_QUERY_STRING' => '', 'REDIRECT_URL' => '', 'SCRIPT_FILENAME' => '', 'REMOTE_ADDR' => '', 'HTTP_COOKIE' => '', 'HTTP_USER_AGENT' => '', 'SCRIPT_URI' => ''))));
 
-	if(isset($_POST) && sizeof($_POST) > 0){
+	if(sizeof($_POST) > 0){
 		$errorString .= "POST DATA:\n";
 		$errorString .= vds($_POST);
 	}
diff --git a/lib/Ebook.php b/lib/Ebook.php
index c042230b..0c54c098 100644
--- a/lib/Ebook.php
+++ b/lib/Ebook.php
@@ -41,7 +41,7 @@ class Ebook{
 	public $TitleWithCreditsHtml = '';
 	public $Timestamp;
 
-	public function __construct($wwwFilesystemPath){
+	public function __construct(string $wwwFilesystemPath){
 		// First, construct a source repo path from our WWW filesystem path.
 		$this->RepoFilesystemPath = str_replace(SITE_ROOT . '/www/ebooks/', '', $wwwFilesystemPath);
 		$this->RepoFilesystemPath = SITE_ROOT . '/ebooks/' . str_replace('/', '_', $this->RepoFilesystemPath) . '.git';
@@ -65,14 +65,14 @@ class Ebook{
 		$this->WwwFilesystemPath = $wwwFilesystemPath;
 		$this->Url = str_replace(SITE_ROOT . '/www', '', $this->WwwFilesystemPath);
 
-		$rawMetadata = file_get_contents($wwwFilesystemPath . '/src/epub/content.opf');
+		$rawMetadata = file_get_contents($wwwFilesystemPath . '/src/epub/content.opf') ?: '';
 
 		// Get the SE identifier.
 		preg_match('|<dc:identifier[^>]*?>(.+?)</dc:identifier>|ius', $rawMetadata, $matches);
 		if(sizeof($matches) != 2){
 			throw new EbookParsingException('Invalid <dc:identifier> element.');
 		}
-		$this->Identifier = $matches[1];
+		$this->Identifier = (string)$matches[1];
 
 		$this->UrlSafeIdentifier = str_replace(['url:https://standardebooks.org/ebooks/', '/'], ['', '_'], $this->Identifier);
 
@@ -114,7 +114,7 @@ class Ebook{
 		}
 
 		// Fill in the short history of this repo.
-		$historyEntries = explode("\n", shell_exec('cd ' . escapeshellarg($this->RepoFilesystemPath) . ' && git log -n5 --pretty=format:"%ct %s"'));
+		$historyEntries = explode("\n", shell_exec('cd ' . escapeshellarg($this->RepoFilesystemPath) . ' && git log -n5 --pretty=format:"%ct %s"') ?? '');
 
 		foreach($historyEntries as $entry){
 			$array = explode(' ', $entry, 2);
@@ -133,7 +133,7 @@ class Ebook{
 		$this->HeroImage2xUrl = '/images/covers/' . $this->UrlSafeIdentifier . '-' . $hash . '-hero@2x.jpg';
 
 		// Now do some heavy XML lifting!
-		$xml = new SimpleXmlElement(str_replace('xmlns=', 'ns=', $rawMetadata));
+		$xml = new SimpleXMLElement(str_replace('xmlns=', 'ns=', $rawMetadata));
 		$xml->registerXPathNamespace('dc', 'http://purl.org/dc/elements/1.1/');
 
 		$this->Title = $this->NullIfEmpty($xml->xpath('/package/metadata/dc:title'));
@@ -148,17 +148,17 @@ class Ebook{
 		$this->Timestamp = new \DateTime((string)$xml->xpath('/package/metadata/dc:date')[0]);
 
 		// Get SE tags
-		foreach($xml->xpath('/package/metadata/meta[@property="meta-auth"]') as $tag){
+		foreach($xml->xpath('/package/metadata/meta[@property="meta-auth"]') ?: [] as $tag){
 			$this->Tags[] = (string)$tag;
 		}
 
 		// Get LoC tags
-		foreach($xml->xpath('/package/metadata/dc:subject') as $tag){
+		foreach($xml->xpath('/package/metadata/dc:subject') ?: [] as $tag){
 			$this->LocTags[] = (string)$tag;
 		}
 
 		// Figure out authors and contributors.
-		foreach($xml->xpath('/package/metadata/dc:creator') as $author){
+		foreach($xml->xpath('/package/metadata/dc:creator') ?: [] as $author){
 			$id = $author->attributes()->id;
 			$this->Authors[] = new Contributor(	(string)$author,
 								(string)$xml->xpath('/package/metadata/meta[@property="file-as"][@refines="#' . $id . '"]')[0],
@@ -173,9 +173,9 @@ class Ebook{
 
 		$this->AuthorsUrl = preg_replace('|url:https://standardebooks.org/ebooks/([^/]+)/.*|ius', '/ebooks/\1/', $this->Identifier);
 
-		foreach($xml->xpath('/package/metadata/dc:contributor') as $contributor){
+		foreach($xml->xpath('/package/metadata/dc:contributor') ?: [] as $contributor){
 			$id = $contributor->attributes()->id;
-			foreach($xml->xpath('/package/metadata/meta[@property="role"][@refines="#' . $id . '"]') as $role){
+			foreach($xml->xpath('/package/metadata/meta[@property="role"][@refines="#' . $id . '"]') ?: [] as $role){
 				$c = new Contributor(
 							(string)$contributor,
 							$this->NullIfEmpty($xml->xpath('/package/metadata/meta[@property="file-as"][@refines="#' . $id . '"]')),
@@ -266,7 +266,7 @@ class Ebook{
 		$this->WikipediaUrl = $this->NullIfEmpty($xml->xpath('/package/metadata/meta[@property="se:url.encyclopedia.wikipedia"][not(@refines)]'));
 
 		// Next the page scan source URLs.
-		foreach($xml->xpath('/package/metadata/dc:source') as $element){
+		foreach($xml->xpath('/package/metadata/dc:source') ?: [] as $element){
 			if(mb_stripos((string)$element, '//www.gutenberg.org/') !== false){
 				$this->SourceUrls[] = ['source' => SOURCE_PROJECT_GUTENBERG, 'url' => (string)$element];
 			}
@@ -335,8 +335,8 @@ class Ebook{
 		}
 
 		// Remove diacritics and non-alphanumeric characters
-		$searchString = trim(preg_replace('|[^a-zA-Z0-9 ]|ius', ' ', @iconv('UTF-8', 'ASCII//TRANSLIT', $searchString)));
-		$query = trim(preg_replace('|[^a-zA-Z0-9 ]|ius', ' ', @iconv('UTF-8', 'ASCII//TRANSLIT', $query)));
+		$searchString = trim(preg_replace('|[^a-zA-Z0-9 ]|ius', ' ', iconv('UTF-8', 'ASCII//TRANSLIT', $searchString) ?: '') ?? '');
+		$query = trim(preg_replace('|[^a-zA-Z0-9 ]|ius', ' ', iconv('UTF-8', 'ASCII//TRANSLIT', $query) ?: '') ?? '');
 
 		if($query == ''){
 			return false;
@@ -428,7 +428,7 @@ class Ebook{
 			}
 		}
 
-		return json_encode($output, JSON_PRETTY_PRINT);
+		return json_encode($output, JSON_PRETTY_PRINT) ?: '';
 	}
 
 	private function GenerateContributorJsonLd(Contributor $contributor): stdClass{
@@ -476,7 +476,11 @@ class Ebook{
 		return $string;
 	}
 
-	private function NullIfEmpty(array $elements){ // Can't use type hinting until PHP 7.1 which supports nullable return types
+	private function NullIfEmpty($elements): ?string{
+		if($elements === false){
+			return null;
+		}
+
 		// Helper function when getting values from SimpleXml.
 		// Checks if the result is set, and returns the value if so; if the value is the empty string, return null.
 		if(isset($elements[0])){
diff --git a/lib/Formatter.php b/lib/Formatter.php
index b951c826..541e328e 100644
--- a/lib/Formatter.php
+++ b/lib/Formatter.php
@@ -2,19 +2,19 @@
 class Formatter{
 	public static function MakeUrlSafe(string $text): string{
 		// Remove accent characters
-		$text = @iconv('UTF-8', 'ASCII//TRANSLIT', $text);
+		$text = iconv('UTF-8', 'ASCII//TRANSLIT', $text) ?: '';
 
 		// Trim and convert to lowercase
 		$text = mb_strtolower(trim($text));
 
 		// Remove apostrophes
-		$text = preg_replace("/['’]/ius", '', $text);
+		$text = preg_replace("/['’]/ius", '', $text) ?: '';
 
 		// Then convert any non-digit, non-letter character to a space
-		$text = preg_replace('/[^0-9a-zA-Z]/ius', ' ', $text);
+		$text = preg_replace('/[^0-9a-zA-Z]/ius', ' ', $text) ?: '';
 
 		// Then convert any instance of one or more space to dash
-		$text = preg_replace('/\s+/ius', '-', $text);
+		$text = preg_replace('/\s+/ius', '-', $text) ?: '';
 
 		// Finally, trim dashes
 		$text = trim($text, '-');
diff --git a/lib/HttpInput.php b/lib/HttpInput.php
index 7c90c439..57471191 100644
--- a/lib/HttpInput.php
+++ b/lib/HttpInput.php
@@ -1,6 +1,6 @@
 <?
 class HttpInput{
-	public static function GetString(string $variable, bool $allowEmptyString = true, $default = null){ // Can't type hint return values because it might return null
+	public static function GetString(string $variable, bool $allowEmptyString = true, $default = null): ?string{
 		$var = self::GetHttpVar($variable, HTTP_VAR_STR, GET, $default);
 
 		if(!$allowEmptyString && $var === ''){
@@ -10,15 +10,15 @@ class HttpInput{
 		return $var;
 	}
 
-	public static function GetInt(string $variable, $default = null){ // Can't type hint return values because it might return null
+	public static function GetInt(string $variable, $default = null): ?int{
 		return self::GetHttpVar($variable, HTTP_VAR_INT, GET, $default);
 	}
 
-	public static function GetBool(string $variable, $default = null){ // Can't type hint return values because it might return null
+	public static function GetBool(string $variable, $default = null): ?bool{
 		return self::GetHttpVar($variable, HTTP_VAR_BOOL, GET, $default);
 	}
 
-	public static function GetDec(string $variable, $default = null){ // Can't type hint return values because it might return null
+	public static function GetDec(string $variable, $default = null): ?float{
 		return self::GetHttpVar($variable, HTTP_VAR_DEC, GET, $default);
 	}
 
diff --git a/lib/Library.php b/lib/Library.php
index 21bf592a..8b4ffdb1 100644
--- a/lib/Library.php
+++ b/lib/Library.php
@@ -49,7 +49,7 @@ class Library{
 				$ebooks = apcu_fetch('ebooks', $success);
 
 				if(!$success){
-					foreach(explode("\n", trim(shell_exec('find ' . SITE_ROOT . '/www/ebooks/ -name "content.opf"'))) as $filename){
+					foreach(explode("\n", trim(shell_exec('find ' . SITE_ROOT . '/www/ebooks/ -name "content.opf"') ?? '')) as $filename){
 						$ebookWwwFilesystemPath = preg_replace('|/src/.+|ius', '', $filename);
 						$ebook = apcu_fetch('ebook-' . $ebookWwwFilesystemPath, $success);
 
@@ -76,7 +76,7 @@ class Library{
 		if(!$success){
 			$ebooks = [];
 
-			foreach(explode("\n", trim(shell_exec('find ' . escapeshellarg($wwwFilesystemPath) . ' -name "content.opf"'))) as $filename){
+			foreach(explode("\n", trim(shell_exec('find ' . escapeshellarg($wwwFilesystemPath) . ' -name "content.opf"') ?? '')) as $filename){
 				try{
 					$ebookWwwFilesystemPath = preg_replace('|/src/.+|ius', '', $filename);
 					$ebook = apcu_fetch('ebook-' . $ebookWwwFilesystemPath, $success);
diff --git a/lib/Logger.php b/lib/Logger.php
index 67bc556d..f1a825f2 100644
--- a/lib/Logger.php
+++ b/lib/Logger.php
@@ -2,6 +2,12 @@
 class Logger{
 	public static function WriteGithubWebhookLogEntry(string $requestId, string $text){
 		$fp = fopen(GITHUB_WEBHOOK_LOG_FILE_PATH, 'a+');
+
+		if($fp === false){
+			self::WriteErrorLogEntry('Could not open log file: ' . GITHUB_WEBHOOK_LOG_FILE_PATH);
+			return;
+		}
+
 		fwrite($fp, gmdate('Y-m-d H:i:s') . "\t" . $requestId . "\t" . $text . "\n");
 		fclose($fp);
 	}
diff --git a/lib/Template.php b/lib/Template.php
index 39cc7c50..150a0223 100644
--- a/lib/Template.php
+++ b/lib/Template.php
@@ -19,7 +19,7 @@ class Template{
 
 		ob_start();
 		eval(' ?>' . $fileContents . '<? ');
-		$contents = ob_get_contents();
+		$contents = ob_get_contents() ?: '';
 		ob_end_clean();
 
 		return $contents;
diff --git a/templates/EbookGrid.php b/templates/EbookGrid.php
index 369ad52d..5525c840 100644
--- a/templates/EbookGrid.php
+++ b/templates/EbookGrid.php
@@ -1,3 +1,9 @@
+<?
+
+if(!isset($ebooks)){
+	$ebooks = [];
+}
+?>
 <ol>
 <? foreach($ebooks as $ebook){ ?>
 	<li>
diff --git a/www/ebooks/ebook.php b/www/ebooks/ebook.php
index e32a7b72..fe3a3e04 100644
--- a/www/ebooks/ebook.php
+++ b/www/ebooks/ebook.php
@@ -153,7 +153,7 @@ catch(\Exception $ex){
 						<? if($source['source'] == SOURCE_INTERNET_ARCHIVE){ ?><a href="<?= Formatter::ToPlainText($source['url']) ?>" class="internet-archive">Page scans at the Internet Archive</a><? } ?>
 						<? if($source['source'] == SOURCE_HATHI_TRUST){ ?><a href="<?= Formatter::ToPlainText($source['url']) ?>" class="hathitrust">Page scans at HathiTrust</a><? } ?>
 						<? if($source['source'] == SOURCE_GOOGLE_BOOKS){ ?><a href="<?= Formatter::ToPlainText($source['url']) ?>" class="google">Page scans at Google Books</a><? } ?>
-						<? if($source['source'] == SOURCE_OTHER){ ?><a href="<?= Formatter::ToPlainText($source['url']) ?>" class="globe"><?= Formatter::ToPlainText(preg_replace(['|https?://(en\.)?|', '|/.+$|'], '', $source['url'])) ?></a><? } ?>
+						<? if($source['source'] == SOURCE_OTHER){ ?><a href="<?= Formatter::ToPlainText($source['url']) ?>" class="globe"><?= Formatter::ToPlainText(preg_replace(['|https?://(en\.)?|', '|/.+$|'], '', $source['url']) ?? '') ?></a><? } ?>
 					</p>
 				</li>
 				<? } ?>
diff --git a/www/webhooks/github.php b/www/webhooks/github.php
index 61c69497..db998f68 100644
--- a/www/webhooks/github.php
+++ b/www/webhooks/github.php
@@ -1,24 +1,24 @@
 <?
 require_once('Core.php');
 
-try{
-	// Get a semi-random ID to identify this request within the log.
-	$requestId = substr(sha1(time() . rand()), 0, 8);
+// Get a semi-random ID to identify this request within the log.
+$requestId = substr(sha1(time() . rand()), 0, 8);
 
+try{
 	Logger::WriteGithubWebhookLogEntry($requestId, 'Received GitHub webhook.');
 
 	if($_SERVER['REQUEST_METHOD'] != 'POST'){
 		throw new WebhookException('Expected HTTP POST.');
 	}
 
-	$post = file_get_contents('php://input');
+	$post = file_get_contents('php://input') ?: '';
 
 	// Validate the GitHub secret.
 	$splitHash = explode('=', $_SERVER['HTTP_X_HUB_SIGNATURE']);
 	$hashAlgorithm = $splitHash[0];
 	$hash = $splitHash[1];
 
-	if(!hash_equals($hash, hash_hmac($hashAlgorithm, $post, preg_replace("/[\r\n]/ius", '', file_get_contents(GITHUB_SECRET_FILE_PATH))))){
+	if(!hash_equals($hash, hash_hmac($hashAlgorithm, $post, preg_replace("/[\r\n]/ius", '', file_get_contents(GITHUB_SECRET_FILE_PATH) ?: '')))){
 		throw new WebhookException('Invalid GitHub webhook secret.', $post);
 	}
 
@@ -65,7 +65,7 @@ try{
 			// Check the local repo's last commit. If it matches this push, then don't do anything; we're already up to date.
 			$lastCommitSha1 = trim(shell_exec('git -C ' . escapeshellarg($dir) . ' rev-parse HEAD 2>&1; echo $?'));
 
-			if($lastCommitSha1 === null){
+			if($lastCommitSha1 == ''){
 				Logger::WriteGithubWebhookLogEntry($requestId, 'Error getting last local commit. Output: ' . $lastCommitSha1);
 				throw new WebhookException('Couldn\'t process ebook.', $post);
 			}