diff --git a/src/Dibi/Drivers/FirebirdDriver.php b/src/Dibi/Drivers/FirebirdDriver.php
index 77e90ae3..34f06081 100644
--- a/src/Dibi/Drivers/FirebirdDriver.php
+++ b/src/Dibi/Drivers/FirebirdDriver.php
@@ -123,6 +123,7 @@ class FirebirdDriver implements Dibi\Driver, Dibi\ResultDriver, Dibi\Reflector
 		} elseif (is_resource($res)) {
 			return $this->createResultDriver($res);
 		}
+		return NULL;
 	}
 
 
@@ -286,7 +287,7 @@ class FirebirdDriver implements Dibi\Driver, Dibi\ResultDriver, Dibi\Reflector
 	 */
 	public function escapeBool($value)
 	{
-		return $value ? 1 : 0;
+		return $value ? '1' : '0';
 	}
 
 
diff --git a/src/Dibi/Drivers/MsSqlDriver.php b/src/Dibi/Drivers/MsSqlDriver.php
index bd39de38..c6b81c22 100644
--- a/src/Dibi/Drivers/MsSqlDriver.php
+++ b/src/Dibi/Drivers/MsSqlDriver.php
@@ -98,6 +98,7 @@ class MsSqlDriver implements Dibi\Driver, Dibi\ResultDriver
 		} elseif (is_resource($res)) {
 			return $this->createResultDriver($res);
 		}
+		return NULL;
 	}
 
 
@@ -236,7 +237,7 @@ class MsSqlDriver implements Dibi\Driver, Dibi\ResultDriver
 	 */
 	public function escapeBool($value)
 	{
-		return $value ? 1 : 0;
+		return $value ? '1' : '0';
 	}
 
 
diff --git a/src/Dibi/Drivers/MySqliDriver.php b/src/Dibi/Drivers/MySqliDriver.php
index b83acfca..2b50619b 100644
--- a/src/Dibi/Drivers/MySqliDriver.php
+++ b/src/Dibi/Drivers/MySqliDriver.php
@@ -158,6 +158,7 @@ class MySqliDriver implements Dibi\Driver, Dibi\ResultDriver
 		} elseif (is_object($res)) {
 			return $this->createResultDriver($res);
 		}
+		return NULL;
 	}
 
 
@@ -328,7 +329,7 @@ class MySqliDriver implements Dibi\Driver, Dibi\ResultDriver
 	 */
 	public function escapeBool($value)
 	{
-		return $value ? 1 : 0;
+		return $value ? '1' : '0';
 	}
 
 
diff --git a/src/Dibi/Drivers/OdbcDriver.php b/src/Dibi/Drivers/OdbcDriver.php
index 6ba27a38..ff07034d 100644
--- a/src/Dibi/Drivers/OdbcDriver.php
+++ b/src/Dibi/Drivers/OdbcDriver.php
@@ -110,6 +110,7 @@ class OdbcDriver implements Dibi\Driver, Dibi\ResultDriver, Dibi\Reflector
 			$this->affectedRows = odbc_num_rows($res);
 			return $this->createResultDriver($res);
 		}
+		return NULL;
 	}
 
 
@@ -260,7 +261,7 @@ class OdbcDriver implements Dibi\Driver, Dibi\ResultDriver, Dibi\Reflector
 	 */
 	public function escapeBool($value)
 	{
-		return $value ? 1 : 0;
+		return $value ? '1' : '0';
 	}
 
 
diff --git a/src/Dibi/Drivers/OracleDriver.php b/src/Dibi/Drivers/OracleDriver.php
index a522a36a..fb7ff8f7 100644
--- a/src/Dibi/Drivers/OracleDriver.php
+++ b/src/Dibi/Drivers/OracleDriver.php
@@ -123,6 +123,7 @@ class OracleDriver implements Dibi\Driver, Dibi\ResultDriver, Dibi\Reflector
 			$err = oci_error($this->connection);
 			throw new Dibi\DriverException($err['message'], $err['code'], $sql);
 		}
+		return NULL;
 	}
 
 
@@ -284,7 +285,7 @@ class OracleDriver implements Dibi\Driver, Dibi\ResultDriver, Dibi\Reflector
 	 */
 	public function escapeBool($value)
 	{
-		return $value ? 1 : 0;
+		return $value ? '1' : '0';
 	}
 
 
diff --git a/src/Dibi/Drivers/PdoDriver.php b/src/Dibi/Drivers/PdoDriver.php
index f41de79f..483d860b 100644
--- a/src/Dibi/Drivers/PdoDriver.php
+++ b/src/Dibi/Drivers/PdoDriver.php
@@ -40,7 +40,7 @@ class PdoDriver implements Dibi\Driver, Dibi\ResultDriver
 	private $driverName;
 
 	/** @var string */
-	private $serverVersion;
+	private $serverVersion = '';
 
 
 	/**
@@ -112,7 +112,7 @@ class PdoDriver implements Dibi\Driver, Dibi\ResultDriver
 		if (isset($list[$cmd])) {
 			$this->affectedRows = $this->connection->exec($sql);
 			if ($this->affectedRows !== FALSE) {
-				return;
+				return NULL;
 			}
 		} else {
 			$res = $this->connection->query($sql);
@@ -321,7 +321,7 @@ class PdoDriver implements Dibi\Driver, Dibi\ResultDriver
 		if ($this->driverName === 'pgsql') {
 			return $value ? 'TRUE' : 'FALSE';
 		} else {
-			return $value ? 1 : 0;
+			return $value ? '1' : '0';
 		}
 	}
 
diff --git a/src/Dibi/Drivers/PostgreDriver.php b/src/Dibi/Drivers/PostgreDriver.php
index 1b307e95..2259185c 100644
--- a/src/Dibi/Drivers/PostgreDriver.php
+++ b/src/Dibi/Drivers/PostgreDriver.php
@@ -145,6 +145,7 @@ class PostgreDriver implements Dibi\Driver, Dibi\ResultDriver, Dibi\Reflector
 				return $this->createResultDriver($res);
 			}
 		}
+		return NULL;
 	}
 
 
diff --git a/src/Dibi/Drivers/Sqlite3Driver.php b/src/Dibi/Drivers/Sqlite3Driver.php
index a6d4b8ff..a8a1d180 100644
--- a/src/Dibi/Drivers/Sqlite3Driver.php
+++ b/src/Dibi/Drivers/Sqlite3Driver.php
@@ -118,6 +118,7 @@ class Sqlite3Driver implements Dibi\Driver, Dibi\ResultDriver
 		} elseif ($res instanceof \SQLite3Result) {
 			return $this->createResultDriver($res);
 		}
+		return NULL;
 	}
 
 
@@ -280,7 +281,7 @@ class Sqlite3Driver implements Dibi\Driver, Dibi\ResultDriver
 	 */
 	public function escapeBool($value)
 	{
-		return $value ? 1 : 0;
+		return $value ? '1' : '0';
 	}
 
 
diff --git a/src/Dibi/Drivers/SqlsrvDriver.php b/src/Dibi/Drivers/SqlsrvDriver.php
index b9ad53f6..4c20222e 100644
--- a/src/Dibi/Drivers/SqlsrvDriver.php
+++ b/src/Dibi/Drivers/SqlsrvDriver.php
@@ -42,7 +42,7 @@ class SqlsrvDriver implements Dibi\Driver, Dibi\ResultDriver
 	private $affectedRows = FALSE;
 
 	/** @var string */
-	private $version;
+	private $version = '';
 
 
 	/**
@@ -122,6 +122,7 @@ class SqlsrvDriver implements Dibi\Driver, Dibi\ResultDriver
 			$this->affectedRows = sqlsrv_rows_affected($res);
 			return $this->createResultDriver($res);
 		}
+		return NULL;
 	}
 
 
@@ -260,7 +261,7 @@ class SqlsrvDriver implements Dibi\Driver, Dibi\ResultDriver
 	 */
 	public function escapeBool($value)
 	{
-		return $value ? 1 : 0;
+		return $value ? '1' : '0';
 	}
 
 
@@ -334,7 +335,7 @@ class SqlsrvDriver implements Dibi\Driver, Dibi\ResultDriver
 		if ($limit < 0 || $offset < 0) {
 			throw new Dibi\NotSupportedException('Negative offset or limit.');
 
-		} elseif (version_compare($this->version, 11, '<')) { // 11 == SQL Server 2012
+		} elseif (version_compare($this->version, '11', '<')) { // 11 == SQL Server 2012
 			if ($offset) {
 				throw new Dibi\NotSupportedException('Offset is not supported by this database.');
 
diff --git a/src/Dibi/Helpers.php b/src/Dibi/Helpers.php
index ac5d67be..63fe7ab7 100644
--- a/src/Dibi/Helpers.php
+++ b/src/Dibi/Helpers.php
@@ -50,14 +50,14 @@ class Helpers
 				if ($i === 0) {
 					echo "\n<table class=\"dump\">\n<thead>\n\t<tr>\n\t\t<th>#row</th>\n";
 					foreach ($row as $col => $foo) {
-						echo "\t\t<th>" . htmlSpecialChars($col) . "</th>\n";
+						echo "\t\t<th>" . htmlSpecialChars((string) $col) . "</th>\n";
 					}
 					echo "\t</tr>\n</thead>\n<tbody>\n";
 				}
 
 				echo "\t<tr>\n\t\t<th>", $i, "</th>\n";
 				foreach ($row as $col) {
-					echo "\t\t<td>", htmlSpecialChars($col), "</td>\n";
+					echo "\t\t<td>", htmlSpecialChars((string) $col), "</td>\n";
 				}
 				echo "\t</tr>\n";
 			}
diff --git a/src/Dibi/Result.php b/src/Dibi/Result.php
index 79921dcd..6019b589 100644
--- a/src/Dibi/Result.php
+++ b/src/Dibi/Result.php
@@ -271,7 +271,7 @@ class Result implements IDataSource
 		}
 
 		$data = NULL;
-		$assoc = preg_split('#(\[\]|->|=|\|)#', $assoc, NULL, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
+		$assoc = preg_split('#(\[\]|->|=|\|)#', $assoc, -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);
 
 		// check columns
 		foreach ($assoc as $as) {
@@ -499,7 +499,7 @@ class Result implements IDataSource
 					: $tmp;
 
 			} elseif ($type === Type::FLOAT) {
-				$value = ltrim($value, '0');
+				$value = ltrim((string) $value, '0');
 				$p = strpos($value, '.');
 				if ($p !== FALSE) {
 					$value = rtrim(rtrim($value, '0'), '.');
diff --git a/src/Dibi/Translator.php b/src/Dibi/Translator.php
index 13cf13ed..ce08e0ea 100644
--- a/src/Dibi/Translator.php
+++ b/src/Dibi/Translator.php
@@ -246,7 +246,7 @@ final class Translator
 				case 'in':// replaces scalar %in modifier!
 				case 'l': // (val, val, ...)
 					foreach ($value as $k => $v) {
-						$pair = explode('%', $k, 2); // split into identifier & modifier
+						$pair = explode('%', (string) $k, 2); // split into identifier & modifier
 						$vx[] = $this->formatValue($v, isset($pair[1]) ? $pair[1] : (is_array($v) ? 'ex' : FALSE));
 					}
 					return '(' . (($vx || $modifier === 'l') ? implode(', ', $vx) : 'NULL') . ')';
@@ -326,7 +326,7 @@ final class Translator
 
 			switch ($modifier) {
 				case 's':  // string
-					return $value === NULL ? 'NULL' : $this->driver->escapeText($value);
+					return $value === NULL ? 'NULL' : $this->driver->escapeText((string) $value);
 
 				case 'bin':// binary
 					return $value === NULL ? 'NULL' : $this->driver->escapeBinary($value);
@@ -336,7 +336,7 @@ final class Translator
 
 				case 'sN': // string or NULL
 				case 'sn':
-					return $value == '' ? 'NULL' : $this->driver->escapeText($value); // notice two equal signs
+					return $value == '' ? 'NULL' : $this->driver->escapeText((string) $value); // notice two equal signs
 
 				case 'in': // deprecated
 					trigger_error('Modifier %in is deprecated, use %iN.', E_USER_DEPRECATED);
diff --git a/src/Dibi/dibi.php b/src/Dibi/dibi.php
index c4b3e8b6..5112507c 100644
--- a/src/Dibi/dibi.php
+++ b/src/Dibi/dibi.php
@@ -90,7 +90,7 @@ class dibi
 	 * @return Dibi\Connection
 	 * @throws Dibi\Exception
 	 */
-	public static function connect($config = [], $name = 0)
+	public static function connect($config = [], $name = '0')
 	{
 		return self::$connection = self::$registry[$name] = new Dibi\Connection($config, $name);
 	}
diff --git a/src/Dibi/exceptions.php b/src/Dibi/exceptions.php
index a02ae7f2..4a8f7fb6 100644
--- a/src/Dibi/exceptions.php
+++ b/src/Dibi/exceptions.php
@@ -23,7 +23,7 @@ class Exception extends \Exception
 	 * @param  mixed
 	 * @param  string  SQL command
 	 */
-	public function __construct($message = NULL, $code = 0, $sql = NULL)
+	public function __construct($message = '', $code = 0, $sql = NULL)
 	{
 		parent::__construct($message);
 		$this->code = $code;
diff --git a/tests/dibi/Connection.connect.phpt b/tests/dibi/Connection.connect.phpt
index 16da29f4..cf872ca7 100644
--- a/tests/dibi/Connection.connect.phpt
+++ b/tests/dibi/Connection.connect.phpt
@@ -29,7 +29,7 @@ test(function () use ($config) { // lazy
 
 
 test(function () use ($config) { // query string
-	$conn = new Connection(http_build_query($config, NULL, '&'));
+	$conn = new Connection(http_build_query($config, '', '&'));
 	Assert::true($conn->isConnected());
 
 	Assert::null($conn->getConfig('lazy'));