diff --git a/ykval-common.php b/ykval-common.php
index f7f28ee..7200f3c 100644
--- a/ykval-common.php
+++ b/ykval-common.php
@@ -81,7 +81,7 @@ function sign($a, $apiKey, $logger)
 	$qs = utf8_encode($qs);
 
 	// base64 encoded binary digest
-	$hmac = hash_hmac('sha1', $qs, $apiKey, TRUE);
+	$hmac = hash_hmac('sha1', $qs, $apiKey, true);
 	$hmac = base64_encode($hmac);
 
 	$logger->log(LOG_DEBUG, "SIGN: $qs H=$hmac");
@@ -96,17 +96,17 @@ function curl_settings($logger, $ident, $ch, $url, $timeout, $opts)
 	curl_setopt($ch, CURLOPT_URL, $url);
 	curl_setopt($ch, CURLOPT_TIMEOUT, $timeout);
 	curl_setopt($ch, CURLOPT_USERAGENT, 'YK-VAL');
-	curl_setopt($ch, CURLOPT_RETURNTRANSFER, TRUE);
-	curl_setopt($ch, CURLOPT_FAILONERROR, TRUE);
+	curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+	curl_setopt($ch, CURLOPT_FAILONERROR, true);
 
-	if (is_array($opts) === FALSE)
+	if (is_array($opts) === false)
 	{
 		$logger->log(LOG_WARN, $ident . 'curl options must be an array');
 		return;
 	}
 
 	foreach ($opts as $key => $val)
-		if (curl_setopt($ch, $key, $val) === FALSE)
+		if (curl_setopt($ch, $key, $val) === false)
 			$logger->log(LOG_WARN, "$ident failed to set " . curl_opt_name($key));
 }
 
@@ -120,10 +120,10 @@ function curl_opt_name($opt)
 	$consts = get_defined_constants(true);
 	$consts = $consts['curl'];
 
-	$name = array_search($opt, $consts, TRUE);
+	$name = array_search($opt, $consts, true);
 
 	// array_search may return either on failure...
-	if ($name === FALSE || $name === NULL)
+	if ($name === false || $name === null)
 		return 'curl option';
 
 	return $name;
@@ -136,7 +136,7 @@ function curl_opt_name($opt)
 // long as one of the URLs given work, data will be returned.  If all
 // URLs fail, data from some URL that did not match parameter $match
 // (defaults to ^OK) is returned, or if all URLs failed, false.
-function retrieveURLasync($ident, $urls, $logger, $ans_req=1, $match="^OK", $returl=False, $timeout=10, $curlopts)
+function retrieveURLasync($ident, $urls, $logger, $ans_req=1, $match="^OK", $returl=false, $timeout=10, $curlopts)
 {
 	$mh = curl_multi_init();
 	$ch = array();
@@ -216,9 +216,9 @@ function retrieveURLasync($ident, $urls, $logger, $ans_req=1, $match="^OK", $ret
 
 function KSMdecryptOTP($urls, $logger, $curlopts)
 {
-	$response = retrieveURLasync('YK-KSM', $urls, $logger, $ans_req=1, $match='^OK', $returl=False, $timeout=10, $curlopts);
+	$response = retrieveURLasync('YK-KSM', $urls, $logger, $ans_req=1, $match='^OK', $returl=false, $timeout=10, $curlopts);
 
-	if ($response === FALSE)
+	if ($response === false)
 		return false;
 
 	$response = array_shift($response);
@@ -242,7 +242,7 @@ function KSMdecryptOTP($urls, $logger, $curlopts)
 
 function sendResp($status, $logger, $apiKey = '', $extra = null)
 {
-	if ($logger->request !== NULL)
+	if ($logger->request !== null)
 		$logger->request->set('status', $status);
 
 	$a['status'] = $status;
@@ -272,7 +272,7 @@ function sendResp($status, $logger, $apiKey = '', $extra = null)
 
 	$logger->log(LOG_INFO, "Response: " . $str . " (at " . gmdate("c") . " " . microtime() . ")");
 
-	if ($logger->request !== NULL)
+	if ($logger->request !== null)
 		$logger->request->write();
 
 	echo $str;
@@ -280,7 +280,7 @@ function sendResp($status, $logger, $apiKey = '', $extra = null)
 }
 
 // backport from PHP 5.6
-if (function_exists('hash_equals') === FALSE)
+if (function_exists('hash_equals') === false)
 {
 	function hash_equals($a, $b)
 	{
@@ -309,27 +309,27 @@ function total_time ($url)
 	$opts = array(
 		CURLOPT_URL => $url,
 		CURLOPT_TIMEOUT => 3,
-		CURLOPT_FORBID_REUSE => TRUE,
-		CURLOPT_FRESH_CONNECT => TRUE,
-		CURLOPT_RETURNTRANSFER => TRUE,
+		CURLOPT_FORBID_REUSE => true,
+		CURLOPT_FRESH_CONNECT => true,
+		CURLOPT_RETURNTRANSFER => true,
 		CURLOPT_USERAGENT => 'ykval-munin-vallatency/1.0',
 	);
 
-	if (($ch = curl_init()) === FALSE)
+	if (($ch = curl_init()) === false)
 		return false;
 
-	if (curl_setopt_array($ch, $opts) === FALSE)
+	if (curl_setopt_array($ch, $opts) === false)
 		return false;
 
 	// we don't care about the actual response
-	if (curl_exec($ch) === FALSE)
+	if (curl_exec($ch) === false)
 		return false;
 
 	$total_time = curl_getinfo($ch, CURLINFO_TOTAL_TIME);
 
 	curl_close($ch);
 
-	if (is_float($total_time) === FALSE)
+	if (is_float($total_time) === false)
 		return false;
 
 	return $total_time;
@@ -355,7 +355,7 @@ function endpoints ($urls)
 		$internal = substr(sha1($url), 0, 20);
 
 		// actual label name shown for graph values
-		if (($label = hostport($url)) === FALSE)
+		if (($label = hostport($url)) === false)
 		{
 			return false;
 		}
@@ -387,20 +387,20 @@ function endpoints ($urls)
  */
 function hostport ($url)
 {
-	if (($url = parse_url($url)) === FALSE)
+	if (($url = parse_url($url)) === false)
 		return false;
 
-	if (array_key_exists('host', $url) === FALSE || $url['host'] === NULL)
+	if (array_key_exists('host', $url) === false || $url['host'] === null)
 		return false;
 
-	if (array_key_exists('port', $url) === TRUE && $url['port'] !== NULL)
+	if (array_key_exists('port', $url) === true && $url['port'] !== null)
 		return $url['host'].':'.$url['port'];
 
-	if (array_key_exists('scheme', $url) === TRUE
+	if (array_key_exists('scheme', $url) === true
 			&& strtolower($url['scheme']) === 'http')
 		return $url['host'].':80';
 
-	if (array_key_exists('scheme', $url) === TRUE
+	if (array_key_exists('scheme', $url) === true
 			&& strtolower($url['scheme']) === 'https')
 		return $url['host'].':443';
 
diff --git a/ykval-db-oci.php b/ykval-db-oci.php
index 834a09d..bbbfece 100644
--- a/ykval-db-oci.php
+++ b/ykval-db-oci.php
@@ -72,7 +72,7 @@ public function connect(){
     if (!$this->dbh) {
       $error = oci_error();
       $this->myLog->log(LOG_CRIT, "Database connection error: " . $error["message"]);
-      $this->dbh=Null;
+      $this->dbh=null;
       return false;
     }
     return true;
@@ -88,7 +88,7 @@ protected function query($query, $returnresult=false) {
       $result = oci_parse($this->dbh, $query);
       if(!oci_execute($result)) {
 	$this->myLog->log(LOG_INFO, 'Database query error: ' . preg_replace('/\n/',' ',print_r(oci_error($result), true)));
-	$this->dbh = Null;
+	$this->dbh = null;
 	return false;
       }
       $this->result = $result;
diff --git a/ykval-db-pdo.php b/ykval-db-pdo.php
index a3a7014..b11b8b6 100644
--- a/ykval-db-pdo.php
+++ b/ykval-db-pdo.php
@@ -71,7 +71,7 @@ public function connect(){
       $this->dbh = new PDO($this->db_dsn, $this->db_username, $this->db_password, $this->db_options);
     } catch (PDOException $e) {
       $this->myLog->log(LOG_CRIT, "Database connection error: " . $e->getMessage());
-      $this->dbh=Null;
+      $this->dbh=null;
       return false;
     }
     return true;
@@ -88,7 +88,7 @@ protected function query($query, $returnresult=false) {
 	$this->result = $this->dbh->query($query);
       } catch (PDOException $e) {
 	$this->myLog->log(LOG_INFO, 'Database query error: ' . preg_replace('/\n/',' ',print_r($this->dbh->errorInfo(), true)));
-	$this->dbh = Null;
+	$this->dbh = null;
 	return false;
       }
       if ($returnresult) return $this->result;
@@ -137,33 +137,33 @@ public function closeCursor($result=null){
 	 *
 	 * @return mixed Array with values from Db row or 2d-array with multiple rows
 	 */
-	public function findByMultiple($table, $where, $nr=NULL, $rev=NULL, $distinct=NULL)
+	public function findByMultiple($table, $where, $nr=null, $rev=null, $distinct=null)
 	{
 		$value = '';
-		$match = NULL;
+		$match = null;
 		$query = 'SELECT';
 
-		if ($distinct != NULL)
+		if ($distinct != null)
 			$query.= " DISTINCT " . $distinct;
 		else
 			$query.= " *";
 
 		$query.= " FROM " . $table;
 
-		if ($where != NULL)
+		if ($where != null)
 		{
 			foreach ($where as $key => $value)
 			{
-				if ($key != NULL)
+				if ($key != null)
 				{
-					if ($value != NULL)
+					if ($value != null)
 						$match .= " ". $key . " = '" . $value . "' and";
 					else
 						$match .= " ". $key . " is NULL and";
 				}
 			}
 
-			if ($match != NULL)
+			if ($match != null)
 				$query .= " WHERE" . $match;
 
 			$query = rtrim($query, "and");
@@ -173,7 +173,7 @@ public function findByMultiple($table, $where, $nr=NULL, $rev=NULL, $distinct=NU
 		if ($rev == 1)
 			$query.= " ORDER BY id DESC";
 
-		if ($nr != NULL)
+		if ($nr != null)
 			$query.= " LIMIT " . $nr;
 
 		$result = $this->query($query, true);
diff --git a/ykval-db.php b/ykval-db.php
index d22551e..d836995 100644
--- a/ykval-db.php
+++ b/ykval-db.php
@@ -93,7 +93,7 @@ public function timestampDeltaTime($first, $second)
    */
   public function disconnect()
   {
-    $this->dbh=NULL;
+    $this->dbh=null;
   }
 
   /**
@@ -104,8 +104,8 @@ public function disconnect()
    */
   public function isConnected()
   {
-    if ($this->dbh!=NULL) return True;
-    else return False;
+    if ($this->dbh!=null) return true;
+    else return false;
   }
 
   /**
diff --git a/ykval-log-verify.php b/ykval-log-verify.php
index 927bc4d..5725580 100644
--- a/ykval-log-verify.php
+++ b/ykval-log-verify.php
@@ -31,27 +31,27 @@
 
 class LogVerify
 {
-	public $format = NULL;
+	public $format = null;
 
 	private $fields = array(
-		'time_start' => NULL,
-		'time_end' => NULL,
-		'time_taken' => NULL,
-		'ip' => NULL,
-		'client' => NULL,
-		'public_id' => NULL,
-		'otp' => NULL,
-		'status' => NULL,
-		'nonce' => NULL,
-		'signed' => NULL,
-		'counter' => NULL,
-		'low' => NULL,
-		'high' => NULL,
-		'use' => NULL,
-		'tls' => NULL,
-		'protocol' => NULL,
-		'sl' => NULL,
-		'timeout' => NULL,
+		'time_start' => null,
+		'time_end' => null,
+		'time_taken' => null,
+		'ip' => null,
+		'client' => null,
+		'public_id' => null,
+		'otp' => null,
+		'status' => null,
+		'nonce' => null,
+		'signed' => null,
+		'counter' => null,
+		'low' => null,
+		'high' => null,
+		'use' => null,
+		'tls' => null,
+		'protocol' => null,
+		'sl' => null,
+		'timeout' => null,
 	);
 
 	/**
@@ -67,7 +67,7 @@ public function set($name, $value)
 		if ($name === 'time_end' || $name === 'time_taken')
 			return false;
 
-		if (array_key_exists($name, $this->fields) === FALSE)
+		if (array_key_exists($name, $this->fields) === false)
 			return false;
 
 		$this->fields[$name] = $value;
@@ -81,7 +81,7 @@ public function set($name, $value)
 	 */
 	public function write()
 	{
-		if ($this->format === NULL)
+		if ($this->format === null)
 			return false;
 
 		$values = array();
@@ -127,25 +127,25 @@ private function sanitized()
 		if (preg_match('/^[0-9]+$/', $a['client']) !== 1)
 			$a['client'] = '-';
 
-		if (filter_var($a['ip'], FILTER_VALIDATE_IP) === FALSE)
+		if (filter_var($a['ip'], FILTER_VALIDATE_IP) === false)
 			$a['ip'] = '-';
 
-		if (is_int($a['counter']) === FALSE)
+		if (is_int($a['counter']) === false)
 			$a['counter'] = '-';
 
-		if (is_int($a['low']) === FALSE)
+		if (is_int($a['low']) === false)
 			$a['low'] = '-';
 
-		if (is_int($a['high']) === FALSE)
+		if (is_int($a['high']) === false)
 			$a['high'] = '-';
 
-		if (is_int($a['use']) === FALSE)
+		if (is_int($a['use']) === false)
 			$a['use'] = '-';
 
 		if (preg_match('/^[a-zA-Z0-9]{16,40}$/', $a['nonce']) !== 1)
 			$a['nonce'] = '-';
 
-		if (is_float($a['protocol']) === TRUE)
+		if (is_float($a['protocol']) === true)
 			$a['protocol'] = sprintf('%.1f', $a['protocol']);
 		else
 			$a['protocol'] = '-';
diff --git a/ykval-log.php b/ykval-log.php
index 20502f3..4c46f8d 100644
--- a/ykval-log.php
+++ b/ykval-log.php
@@ -30,7 +30,7 @@
 class Log
 {
 	// request logger object
-	public $request = NULL;
+	public $request = null;
 
 	private $log_levels = array(
 			LOG_EMERG => 'LOG_EMERG',
@@ -57,7 +57,7 @@ public function addField ($name, $value)
 		$this->fields[$name] = $value;
 	}
 
-	public function log ($priority, $message, $extra = NULL)
+	public function log ($priority, $message, $extra = null)
 	{
 		$prefix = '';
 		foreach ($this->fields as $val)
diff --git a/ykval-munin-ksmlatency.php b/ykval-munin-ksmlatency.php
index 450121c..6cc1ce1 100755
--- a/ykval-munin-ksmlatency.php
+++ b/ykval-munin-ksmlatency.php
@@ -41,7 +41,7 @@
 # otp and client ID should be moved to a munin environment variable
 $urls = otp2ksmurls('ccccccccfnkjtvvijktfrvvginedlbvudjhjnggndtck', 16);
 
-if (($endpoints = endpoints($urls)) === FALSE)
+if (($endpoints = endpoints($urls)) === false)
 {
 	echo "Cannot parse URLs from ksm url list\n";
 	exit(1);
@@ -81,7 +81,7 @@
 {
 	list ($internal, $label, $url) = $endpoint;
 
-	if (($total_time = total_time($url)) === FALSE)
+	if (($total_time = total_time($url)) === false)
 		$total_time = 'error';
 
 	echo "${internal}_avgwait.value ${total_time}\n";
diff --git a/ykval-munin-queuelength.php b/ykval-munin-queuelength.php
index e7ce582..79baa67 100755
--- a/ykval-munin-queuelength.php
+++ b/ykval-munin-queuelength.php
@@ -53,7 +53,7 @@
 	exit(0);
 }
 
-if (($endpoints = endpoints($urls)) === FALSE)
+if (($endpoints = endpoints($urls)) === false)
 {
 	echo "Cannot parse URLs from sync pool list\n";
 	exit(1);
diff --git a/ykval-munin-vallatency.php b/ykval-munin-vallatency.php
index 7de0abe..1273082 100755
--- a/ykval-munin-vallatency.php
+++ b/ykval-munin-vallatency.php
@@ -52,7 +52,7 @@
 	exit(0);
 }
 
-if (($endpoints = endpoints($urls)) === FALSE)
+if (($endpoints = endpoints($urls)) === false)
 {
 	echo "Cannot parse URLs from sync pool list\n";
 	exit(1);
@@ -86,7 +86,7 @@
 {
 	list ($internal, $label, $url) = $endpoint;
 
-	if (($total_time = total_time($url)) === FALSE)
+	if (($total_time = total_time($url)) === false)
 		$total_time = 'error';
 
 	echo "${internal}_avgwait.value ${total_time}\n";
diff --git a/ykval-munin-yubikeystats.php b/ykval-munin-yubikeystats.php
index 0d0a76a..ee25995 100755
--- a/ykval-munin-yubikeystats.php
+++ b/ykval-munin-yubikeystats.php
@@ -81,7 +81,7 @@ function get_count($db, $table, $conditions)
 		return $r['count'];
 	}
 
-	return Null;
+	return null;
 }
 
 if ($count = get_count($db, 'yubikeys', 'active=true'))
diff --git a/ykval-resync.php b/ykval-resync.php
index 9913d7f..7ccab46 100644
--- a/ykval-resync.php
+++ b/ykval-resync.php
@@ -84,7 +84,7 @@
 }
 
 foreach($yubikeys as $key) {
-  if (($localParams = $sync->getLocalParams($key)) === FALSE) {
+  if (($localParams = $sync->getLocalParams($key)) === false) {
     logdie($myLog, 'ERROR Invalid Yubikey ' . $key);
   }
 
diff --git a/ykval-sync.php b/ykval-sync.php
index b9520a4..bc42b92 100644
--- a/ykval-sync.php
+++ b/ykval-sync.php
@@ -47,7 +47,7 @@
 }
 
 // verify request sent by whitelisted address
-if (in_array($ipaddr, $allowed, TRUE) === FALSE)
+if (in_array($ipaddr, $allowed, true) === false)
 {
 	$myLog->log(LOG_NOTICE, "Operation not allowed from IP $ipaddr");
 	$myLog->log(LOG_DEBUG, "Remote IP $ipaddr not listed in allowed sync pool : " . implode(', ', $allowed));
@@ -56,23 +56,23 @@
 
 // define requirements on protocol
 $syncParams = array(
-	'modified' => NULL,
-	'otp' => NULL,
-	'nonce' => NULL,
-	'yk_publicname' => NULL,
-	'yk_counter' => NULL,
-	'yk_use' => NULL,
-	'yk_high' => NULL,
-	'yk_low' => NULL
+	'modified' => null,
+	'otp' => null,
+	'nonce' => null,
+	'yk_publicname' => null,
+	'yk_counter' => null,
+	'yk_use' => null,
+	'yk_high' => null,
+	'yk_low' => null
 );
 
 // extract values from HTTP request
 $tmp_log = 'Received ';
 foreach ($syncParams as $param => $value)
 {
-	$value = getHttpVal($param, NULL, $_GET);
+	$value = getHttpVal($param, null, $_GET);
 
-	if ($value == NULL)
+	if ($value == null)
 	{
 		$myLog->log(LOG_NOTICE, "Received request with parameter[s] ($param) missing value");
 		sendResp(S_MISSING_PARAMETER, $myLog);
@@ -114,7 +114,7 @@
 
 // get local counter data
 $yk_publicname = $syncParams['yk_publicname'];
-if (($localParams = $sync->getLocalParams($yk_publicname)) === FALSE)
+if (($localParams = $sync->getLocalParams($yk_publicname)) === false)
 {
 	$myLog->log(LOG_NOTICE, "Invalid Yubikey $yk_publicname");
 	sendResp(S_BACKEND_ERROR, $myLog);
diff --git a/ykval-synclib.php b/ykval-synclib.php
index 2963ccb..db05e2d 100644
--- a/ykval-synclib.php
+++ b/ykval-synclib.php
@@ -150,7 +150,7 @@ public function queue($otpParams, $localParams)
 		return $result;
 	}
 
-	public function log($priority, $msg, $params=NULL)
+	public function log($priority, $msg, $params=null)
 	{
 		if ($params)
 			$msg .= ' modified=' . $params['modified'] .
@@ -466,9 +466,9 @@ public function sync($ans_req, $timeout=1)
 		}
 
 		// send out requests
-		$ans_arr = retrieveURLasync('YK-VAL sync', $urls, $this->myLog, $ans_req, $match='status=OK', $returl=True, $timeout, $this->curlopts);
+		$ans_arr = retrieveURLasync('YK-VAL sync', $urls, $this->myLog, $ans_req, $match='status=OK', $returl=true, $timeout, $this->curlopts);
 
-		if ($ans_arr === FALSE)
+		if ($ans_arr === false)
 		{
 			$this->log(LOG_WARNING, 'No responses from validation server pool');
 			$ans_arr = array();
@@ -542,7 +542,7 @@ public function sync($ans_req, $timeout=1)
 		 * NULL queued_time for remaining entries in queue, to allow
 		 *	daemon to take care of them as soon as possible.
 		 */
-		$this->db->updateBy('queue', 'server_nonce', $this->server_nonce, array('queued'=>NULL));
+		$this->db->updateBy('queue', 'server_nonce', $this->server_nonce, array('queued'=>null));
 
 		/**
 		 * Return true if valid answers equals required answers.
diff --git a/ykval-verify.php b/ykval-verify.php
index bd15013..156d324 100644
--- a/ykval-verify.php
+++ b/ykval-verify.php
@@ -38,8 +38,8 @@
 
 $ipaddr = $_SERVER['REMOTE_ADDR'];
 
-$https = (array_key_exists('HTTPS', $_SERVER) === TRUE
-			&& strtolower($_SERVER['HTTPS']) !== 'off' ? TRUE : FALSE);
+$https = (array_key_exists('HTTPS', $_SERVER) === true
+			&& strtolower($_SERVER['HTTPS']) !== 'off' ? true : false);
 
 $myLog = new Log('ykval-verify');
 $myLog->addField('ip', $ipaddr);
@@ -255,7 +255,7 @@
 	sendResp(S_BACKEND_ERROR, $myLog);
 }
 
-if (($cd = $sync->getClientData($client)) === FALSE)
+if (($cd = $sync->getClientData($client)) === false)
 {
 	$myLog->log(LOG_NOTICE, "Invalid client id $client");
 	sendResp(S_NO_SUCH_CLIENT, $myLog);
@@ -277,7 +277,7 @@
 
 	$hmac = sign($request, $apiKey, $myLog);
 
-	if (hash_equals($hmac, $h) === FALSE)
+	if (hash_equals($hmac, $h) === false)
 	{
 		$myLog->log(LOG_DEBUG, "client hmac=$h, server hmac=$hmac");
 		sendResp(S_BAD_SIGNATURE, $myLog, $apiKey);
@@ -308,7 +308,7 @@
 {
 	$curlopts = $baseParams['__YKVAL_KSM_CURL_OPTS__'];
 }
-if (($otpinfo = KSMdecryptOTP($urls, $myLog, $curlopts)) === FALSE)
+if (($otpinfo = KSMdecryptOTP($urls, $myLog, $curlopts)) === false)
 {
 	/**
 	 * FIXME
@@ -327,7 +327,7 @@
 // get Yubikey from DB
 $public_id = substr($otp, 0, strlen ($otp) - TOKEN_LEN);
 $myLog->request->set('public_id', $public_id);
-if (($localParams = $sync->getLocalParams($public_id)) === FALSE)
+if (($localParams = $sync->getLocalParams($public_id)) === false)
 {
 	$myLog->log(LOG_NOTICE, "Invalid Yubikey $public_id");
 	sendResp(S_BACKEND_ERROR, $myLog, $apiKey);
@@ -414,7 +414,7 @@
 	'timeout' => $timeout,
 ));
 
-if ($syncres == False)
+if ($syncres == false)
 {
 	/* sync returned false, indicating that
 		either at least 1 answer marked OTP as invalid or