diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index 18398b64b74..75e19e91e13 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -1424,7 +1424,7 @@ public function escape_identifiers($item)
 			return $item;
 		}
 		// Avoid breaking functions and literal values inside queries
-		elseif (ctype_digit($item) OR $item[0] === "'" OR ($this->_escape_char !== '"' && $item[0] === '"') OR strpos($item, '(') !== FALSE)
+		elseif (ctype_digit((string) $item) OR $item[0] === "'" OR ($this->_escape_char !== '"' && $item[0] === '"') OR strpos($item, '(') !== FALSE)
 		{
 			return $item;
 		}
diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index 3ff7f40c991..e91612d84af 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -2717,7 +2717,7 @@ protected function _is_literal($str)
 	{
 		$str = trim($str);
 
-		if (empty($str) OR ctype_digit($str) OR (string) (float) $str === $str OR in_array(strtoupper($str), array('TRUE', 'FALSE'), TRUE))
+		if (empty($str) OR ctype_digit((string) $str) OR (string) (float) $str === $str OR in_array(strtoupper($str), array('TRUE', 'FALSE'), TRUE))
 		{
 			return TRUE;
 		}
diff --git a/system/database/drivers/oci8/oci8_driver.php b/system/database/drivers/oci8/oci8_driver.php
index 7bb43b5be8e..0ce8252cf1a 100644
--- a/system/database/drivers/oci8/oci8_driver.php
+++ b/system/database/drivers/oci8/oci8_driver.php
@@ -179,7 +179,7 @@ public function __construct($params)
 			return;
 		}
 		elseif ($this->hostname !== '' && strpos($this->hostname, '/') === FALSE && strpos($this->hostname, ':') === FALSE
-			&& (( ! empty($this->port) && ctype_digit($this->port)) OR $this->database !== ''))
+			&& (( ! empty($this->port) && ctype_digit((string) $this->port)) OR $this->database !== ''))
 		{
 			/* If the hostname field isn't empty, doesn't contain
 			 * ':' and/or '/' and if port and/or database aren't
@@ -189,7 +189,7 @@ public function __construct($params)
 			 * that the database field is a service name.
 			 */
 			$this->dsn = $this->hostname
-				.(( ! empty($this->port) && ctype_digit($this->port)) ? ':'.$this->port : '')
+				.(( ! empty($this->port) && ctype_digit((string) $this->port)) ? ':'.$this->port : '')
 				.($this->database !== '' ? '/'.ltrim($this->database, '/') : '');
 
 			if (preg_match($valid_dsns['ec'], $this->dsn))
diff --git a/system/database/drivers/postgre/postgre_driver.php b/system/database/drivers/postgre/postgre_driver.php
index 15d800b46fd..0cbd1f45715 100644
--- a/system/database/drivers/postgre/postgre_driver.php
+++ b/system/database/drivers/postgre/postgre_driver.php
@@ -95,7 +95,7 @@ protected function _build_dsn()
 
 		$this->hostname === '' OR $this->dsn = 'host='.$this->hostname.' ';
 
-		if ( ! empty($this->port) && ctype_digit($this->port))
+		if ( ! empty($this->port) && ctype_digit((string) $this->port))
 		{
 			$this->dsn .= 'port='.$this->port.' ';
 		}
diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 024f0ed6260..eeb83b99f0c 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -1211,7 +1211,7 @@ public function valid_url($str)
 
 		// Apparently, FILTER_VALIDATE_URL doesn't reject digit-only names for some reason ...
 		// See https://github.com/bcit-ci/CodeIgniter/issues/5755
-		if (ctype_digit($str))
+		if (ctype_digit((string) $str))
 		{
 			return FALSE;
 		}
diff --git a/system/libraries/Image_lib.php b/system/libraries/Image_lib.php
index ea8c56d01be..4c8994c96e1 100644
--- a/system/libraries/Image_lib.php
+++ b/system/libraries/Image_lib.php
@@ -638,7 +638,7 @@ public function initialize($props = array())
 		// Set the quality
 		$this->quality = trim(str_replace('%', '', $this->quality));
 
-		if ($this->quality === '' OR $this->quality === 0 OR ! ctype_digit($this->quality))
+		if ($this->quality === '' OR $this->quality === 0 OR ! ctype_digit((string) $this->quality))
 		{
 			$this->quality = 90;
 		}
diff --git a/system/libraries/Session/Session.php b/system/libraries/Session/Session.php
index a211ce31bf9..03f61e8df9c 100644
--- a/system/libraries/Session/Session.php
+++ b/system/libraries/Session/Session.php
@@ -392,7 +392,7 @@ protected function _configure_sid_length()
 		if (PHP_VERSION_ID < 70100)
 		{
 			$hash_function = ini_get('session.hash_function');
-			if (ctype_digit($hash_function))
+			if (ctype_digit((string) $hash_function))
 			{
 				if ($hash_function !== '1')
 				{