Replace is_null() with === / !== NULL

Exact same behavior, but faster. I also think it's more readable.
diff --git a/system/libraries/Email.php b/system/libraries/Email.php
index 1834be2..3a38645 100644
--- a/system/libraries/Email.php
+++ b/system/libraries/Email.php
@@ -1335,7 +1335,7 @@
 		for ($i = 0, $c = count($this->_attachments), $z = 0; $i < $c; $i++)
 		{
 			$filename = $this->_attachments[$i]['name'][0];
-			$basename = is_null($this->_attachments[$i]['name'][1])
+			$basename = $this->_attachments[$i]['name'][1] === NULL
 				? basename($filename) : $this->_attachments[$i]['name'][1];
 			$ctype = $this->_attachments[$i]['type'];
 			$file_content = '';
diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index c405eb6..bbd0b52 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -511,7 +511,7 @@
 	{
 		foreach ($this->_field_data as $field => $row)
 		{
-			if ( ! is_null($row['postdata']))
+			if ($row['postdata'] !== NULL)
 			{
 				if ($row['is_array'] === FALSE)
 				{
@@ -583,7 +583,7 @@
 
 		// If the field is blank, but NOT required, no further tests are necessary
 		$callback = FALSE;
-		if ( ! in_array('required', $rules) && is_null($postdata))
+		if ( ! in_array('required', $rules) && $postdata === NULL)
 		{
 			// Before we bail out, does the rule contain a callback?
 			if (preg_match('/(callback_\w+(\[.*?\])?)/', implode(' ', $rules), $match))
@@ -598,7 +598,7 @@
 		}
 
 		// Isset Test. Typically this rule will only apply to checkboxes.
-		if (is_null($postdata) && $callback === FALSE)
+		if ($postdata === NULL && $callback === FALSE)
 		{
 			if (in_array('isset', $rules, TRUE) OR in_array('required', $rules))
 			{
diff --git a/system/libraries/Ftp.php b/system/libraries/Ftp.php
index b8729a9..dc6bbd2 100644
--- a/system/libraries/Ftp.php
+++ b/system/libraries/Ftp.php
@@ -266,7 +266,7 @@
 		}
 
 		// Set file permissions if needed
-		if ( ! is_null($permissions))
+		if ($permissions !== NULL)
 		{
 			$this->chmod($path, (int) $permissions);
 		}
@@ -320,7 +320,7 @@
 		}
 
 		// Set file permissions if needed
-		if ( ! is_null($permissions))
+		if ($permissions !== NULL)
 		{
 			$this->chmod($rempath, (int) $permissions);
 		}
diff --git a/system/libraries/Javascript.php b/system/libraries/Javascript.php
index 542a0ec..7f1d855 100644
--- a/system/libraries/Javascript.php
+++ b/system/libraries/Javascript.php
@@ -737,7 +737,7 @@
 	{
 		// JSON data can optionally be passed to this function
 		// either as a database result object or an array, or a user supplied array
-		if ( ! is_null($result))
+		if ($result !== NULL)
 		{
 			if (is_object($result))
 			{
@@ -823,7 +823,7 @@
 	 */
 	protected function _prep_args($result, $is_key = FALSE)
 	{
-		if (is_null($result))
+		if ($result === NULL)
 		{
 			return 'null';
 		}
diff --git a/system/libraries/Table.php b/system/libraries/Table.php
index 8656990..b77fcf1 100644
--- a/system/libraries/Table.php
+++ b/system/libraries/Table.php
@@ -291,7 +291,7 @@
 	{
 		// The table data can optionally be passed to this function
 		// either as a database result object or an array
-		if ( ! is_null($table_data))
+		if ($table_data !== NULL)
 		{
 			if (is_object($table_data))
 			{
diff --git a/system/libraries/Unit_test.php b/system/libraries/Unit_test.php
index de8c9bb..7a67c72 100644
--- a/system/libraries/Unit_test.php
+++ b/system/libraries/Unit_test.php
@@ -356,12 +356,12 @@
 	 */
 	protected function _parse_template()
 	{
-		if ( ! is_null($this->_template_rows))
+		if ($this->_template_rows !== NULL)
 		{
 			return;
 		}
 
-		if (is_null($this->_template) OR ! preg_match('/\{rows\}(.*?)\{\/rows\}/si', $this->_template, $match))
+		if ($this->_template === NULL OR ! preg_match('/\{rows\}(.*?)\{\/rows\}/si', $this->_template, $match))
 		{
 			$this->_default_template();
 			return;
diff --git a/system/libraries/User_agent.php b/system/libraries/User_agent.php
index 542deb7..1f4b2fa 100644
--- a/system/libraries/User_agent.php
+++ b/system/libraries/User_agent.php
@@ -158,7 +158,7 @@
 			$this->agent = trim($_SERVER['HTTP_USER_AGENT']);
 		}
 
-		if ( ! is_null($this->agent) && $this->_load_agent_file())
+		if ($this->agent !== NULL && $this->_load_agent_file())
 		{
 			$this->_compile_data();
 		}
diff --git a/system/libraries/Xmlrpc.php b/system/libraries/Xmlrpc.php
index c3c7690..9e60791 100644
--- a/system/libraries/Xmlrpc.php
+++ b/system/libraries/Xmlrpc.php
@@ -368,7 +368,7 @@
 	 */
 	public function timeout($seconds = 5)
 	{
-		if ( ! is_null($this->client) && is_int($seconds))
+		if ($this->client !== NULL && is_int($seconds))
 		{
 			$this->client->timeout = $seconds;
 		}