diff --git a/src/Utils/Strings.php b/src/Utils/Strings.php
index 41a2e274..8bd7e0f0 100644
--- a/src/Utils/Strings.php
+++ b/src/Utils/Strings.php
@@ -273,6 +273,9 @@ public static function indent(string $s, int $level = 1, string $chars = "\t"):
 
 	/**
 	 * Converts all characters of UTF-8 string to lower case.
+	 * @template T of string
+	 * @param T $s
+	 * @return T
 	 */
 	public static function lower(string $s): string
 	{
@@ -282,6 +285,9 @@ public static function lower(string $s): string
 
 	/**
 	 * Converts the first character of a UTF-8 string to lower case and leaves the other characters unchanged.
+	 * @template T of string
+	 * @param T $s
+	 * @return T
 	 */
 	public static function firstLower(string $s): string
 	{
@@ -291,6 +297,9 @@ public static function firstLower(string $s): string
 
 	/**
 	 * Converts all characters of a UTF-8 string to upper case.
+	 * @template T of string
+	 * @param T $s
+	 * @return T
 	 */
 	public static function upper(string $s): string
 	{
@@ -300,6 +309,9 @@ public static function upper(string $s): string
 
 	/**
 	 * Converts the first character of a UTF-8 string to upper case and leaves the other characters unchanged.
+	 * @template T of string
+	 * @param T $s
+	 * @return T
 	 */
 	public static function firstUpper(string $s): string
 	{
@@ -309,6 +321,9 @@ public static function firstUpper(string $s): string
 
 	/**
 	 * Converts the first character of every word of a UTF-8 string to upper case and the others to lower case.
+	 * @template T of string
+	 * @param T $s
+	 * @return T
 	 */
 	public static function capitalize(string $s): string
 	{
@@ -425,7 +440,7 @@ public static function reverse(string $s): string
 
 
 	/**
-	 * Returns part of $haystack before $nth occurence of $needle or returns null if the needle was not found.
+	 * Returns part of $haystack before $nth occurrence of $needle or returns null if the needle was not found.
 	 * Negative value means searching from the end.
 	 */
 	public static function before(string $haystack, string $needle, int $nth = 1): ?string
@@ -438,7 +453,7 @@ public static function before(string $haystack, string $needle, int $nth = 1): ?
 
 
 	/**
-	 * Returns part of $haystack after $nth occurence of $needle or returns null if the needle was not found.
+	 * Returns part of $haystack after $nth occurrence of $needle or returns null if the needle was not found.
 	 * Negative value means searching from the end.
 	 */
 	public static function after(string $haystack, string $needle, int $nth = 1): ?string
@@ -451,7 +466,7 @@ public static function after(string $haystack, string $needle, int $nth = 1): ?s
 
 
 	/**
-	 * Returns position in characters of $nth occurence of $needle in $haystack or null if the $needle was not found.
+	 * Returns position in characters of $nth occurrence of $needle in $haystack or null if the $needle was not found.
 	 * Negative value of `$nth` means searching from the end.
 	 */
 	public static function indexOf(string $haystack, string $needle, int $nth = 1): ?int
@@ -464,7 +479,7 @@ public static function indexOf(string $haystack, string $needle, int $nth = 1):
 
 
 	/**
-	 * Returns position in characters of $nth occurence of $needle in $haystack or null if the needle was not found.
+	 * Returns position in characters of $nth occurrence of $needle in $haystack or null if the needle was not found.
 	 */
 	private static function pos(string $haystack, string $needle, int $nth = 1): ?int
 	{