diff --git a/builtin-functions/kphp-light/stdlib/system-functions.txt b/builtin-functions/kphp-light/stdlib/system-functions.txt
index 3ec1bcec1e..4c7e9c5fa6 100644
--- a/builtin-functions/kphp-light/stdlib/system-functions.txt
+++ b/builtin-functions/kphp-light/stdlib/system-functions.txt
@@ -1,5 +1,27 @@
 <?php
 
+function ctype_alnum(mixed $text): bool;
+
+function ctype_alpha(mixed $text): bool;
+
+function ctype_cntrl(mixed $text): bool;
+
+function ctype_digit(mixed $text): bool;
+
+function ctype_graph(mixed $text): bool;
+
+function ctype_lower(mixed $text): bool;
+
+function ctype_print(mixed $text): bool;
+
+function ctype_punct(mixed $text): bool;
+
+function ctype_space(mixed $text): bool;
+
+function ctype_upper(mixed $text): bool;
+
+function ctype_xdigit(mixed $text): bool;
+
 function php_uname($mode ::: string = "a"): string;
 
 function posix_getpid(): int;
@@ -49,10 +71,3 @@ function raise_sigsegv () ::: void;
 
 /** @kphp-extern-func-info stub */
 function system($command ::: string, int &$result_code = 0): int;
-
-/** @kphp-extern-func-info stub generation-required */
-function ctype_alnum(mixed $text): bool;
-/** @kphp-extern-func-info stub generation-required */
-function ctype_digit(mixed $text): bool;
-/** @kphp-extern-func-info stub generation-required */
-function ctype_xdigit(mixed $text): bool;
diff --git a/runtime-common/stdlib/string/ctype-functions.h b/runtime-common/stdlib/string/ctype-functions.h
new file mode 100644
index 0000000000..731883e07f
--- /dev/null
+++ b/runtime-common/stdlib/string/ctype-functions.h
@@ -0,0 +1,82 @@
+// Compiler for PHP (aka KPHP)
+// Copyright (c) 2025 LLC «V Kontakte»
+// Distributed under the GPL v3 License, see LICENSE.notice.txt
+
+#pragma once
+
+#include "runtime-common/core/runtime-core.h"
+
+#include <algorithm>
+#include <cctype>
+#include <cstdint>
+
+namespace ctype_impl_ {
+inline bool ctype_impl(const mixed& text, int (*iswhat)(int), bool allow_digits, bool allow_minus) noexcept {
+  if (text.is_string()) {
+    const string& str = text.as_string();
+    if (str.empty()) {
+      return false;
+    }
+    return std::all_of(str.c_str(), str.c_str() + str.size(), [iswhat](uint8_t c) noexcept { return iswhat(c); });
+  }
+
+  if (text.is_int()) {
+    const int64_t i = text.as_int();
+    if (i <= 255 && i >= 0) {
+      return iswhat(i);
+    } else if (i >= -128 && i < 0) {
+      return iswhat(i + 256);
+    } else if (i >= 0) {
+      return allow_digits;
+    } else {
+      return allow_minus;
+    }
+  }
+
+  return false;
+}
+} // namespace ctype_impl_
+
+inline bool f$ctype_alnum(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::isalnum, true, false);
+}
+
+inline bool f$ctype_alpha(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::isalpha, false, false);
+}
+
+inline bool f$ctype_cntrl(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::iscntrl, false, false);
+}
+
+inline bool f$ctype_digit(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::isdigit, true, false);
+}
+
+inline bool f$ctype_graph(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::isgraph, true, true);
+}
+
+inline bool f$ctype_lower(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::islower, false, false);
+}
+
+inline bool f$ctype_print(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::isprint, true, true);
+}
+
+inline bool f$ctype_punct(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::ispunct, false, false);
+}
+
+inline bool f$ctype_space(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::isspace, false, false);
+}
+
+inline bool f$ctype_upper(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::isupper, false, false);
+}
+
+inline bool f$ctype_xdigit(const mixed& text) noexcept {
+  return ctype_impl_::ctype_impl(text, std::isxdigit, true, false);
+}
diff --git a/runtime/ctype.cpp b/runtime/ctype.cpp
deleted file mode 100644
index 6932d35c9b..0000000000
--- a/runtime/ctype.cpp
+++ /dev/null
@@ -1,77 +0,0 @@
-// Compiler for PHP (aka KPHP)
-// Copyright (c) 2020 LLC «V Kontakte»
-// Distributed under the GPL v3 License, see LICENSE.notice.txt
-
-#include "runtime/ctype.h"
-
-#include <algorithm>
-#include <cctype>
-
-static bool ctype_impl(const mixed& text, int (*iswhat)(int), bool allow_digits, bool allow_minus) noexcept {
-  if (text.is_string()) {
-    const string& str = text.as_string();
-    if (str.empty()) {
-      return false;
-    }
-    return std::all_of(str.c_str(), str.c_str() + str.size(), [iswhat](std::uint8_t c) { return iswhat(c); });
-  }
-
-  if (text.is_int()) {
-    const int64_t i = text.as_int();
-    if (i <= 255 && i >= 0) {
-      return iswhat(i);
-    } else if (i >= -128 && i < 0) {
-      return iswhat(i + 256);
-    } else if (i >= 0) {
-      return allow_digits;
-    } else {
-      return allow_minus;
-    }
-  }
-
-  return false;
-}
-
-bool f$ctype_alnum(const mixed& text) noexcept {
-  return ctype_impl(text, std::isalnum, true, false);
-}
-
-bool f$ctype_alpha(const mixed& text) noexcept {
-  return ctype_impl(text, std::isalpha, false, false);
-}
-
-bool f$ctype_cntrl(const mixed& text) noexcept {
-  return ctype_impl(text, std::iscntrl, false, false);
-}
-
-bool f$ctype_digit(const mixed& text) noexcept {
-  return ctype_impl(text, std::isdigit, true, false);
-}
-
-bool f$ctype_graph(const mixed& text) noexcept {
-  return ctype_impl(text, std::isgraph, true, true);
-}
-
-bool f$ctype_lower(const mixed& text) noexcept {
-  return ctype_impl(text, std::islower, false, false);
-}
-
-bool f$ctype_print(const mixed& text) noexcept {
-  return ctype_impl(text, std::isprint, true, true);
-}
-
-bool f$ctype_punct(const mixed& text) noexcept {
-  return ctype_impl(text, std::ispunct, false, false);
-}
-
-bool f$ctype_space(const mixed& text) noexcept {
-  return ctype_impl(text, std::isspace, false, false);
-}
-
-bool f$ctype_upper(const mixed& text) noexcept {
-  return ctype_impl(text, std::isupper, false, false);
-}
-
-bool f$ctype_xdigit(const mixed& text) noexcept {
-  return ctype_impl(text, std::isxdigit, true, false);
-}
diff --git a/runtime/ctype.h b/runtime/ctype.h
deleted file mode 100644
index a62dd67061..0000000000
--- a/runtime/ctype.h
+++ /dev/null
@@ -1,19 +0,0 @@
-// Compiler for PHP (aka KPHP)
-// Copyright (c) 2022 LLC «V Kontakte»
-// Distributed under the GPL v3 License, see LICENSE.notice.txt
-
-#pragma once
-
-#include "runtime-common/core/runtime-core.h"
-
-bool f$ctype_alnum(const mixed& text) noexcept;
-bool f$ctype_alpha(const mixed& text) noexcept;
-bool f$ctype_cntrl(const mixed& text) noexcept;
-bool f$ctype_digit(const mixed& text) noexcept;
-bool f$ctype_graph(const mixed& text) noexcept;
-bool f$ctype_lower(const mixed& text) noexcept;
-bool f$ctype_print(const mixed& text) noexcept;
-bool f$ctype_punct(const mixed& text) noexcept;
-bool f$ctype_space(const mixed& text) noexcept;
-bool f$ctype_upper(const mixed& text) noexcept;
-bool f$ctype_xdigit(const mixed& text) noexcept;
diff --git a/runtime/runtime.cmake b/runtime/runtime.cmake
index 9c161d5864..29a08819de 100644
--- a/runtime/runtime.cmake
+++ b/runtime/runtime.cmake
@@ -70,7 +70,6 @@ prepend(KPHP_RUNTIME_SOURCES ${BASE_DIR}/runtime/
         confdata-global-manager.cpp
         confdata-keys.cpp
         critical_section.cpp
-        ctype.cpp
         curl.cpp
         curl-async.cpp
         env.cpp
diff --git a/tests/phpt/string_functions/012_ctype.php b/tests/phpt/string_functions/012_ctype.php
new file mode 100644
index 0000000000..2263126897
--- /dev/null
+++ b/tests/phpt/string_functions/012_ctype.php
@@ -0,0 +1,79 @@
+@ok
+<?php
+
+var_dump(ctype_alnum("abc123"));
+var_dump(ctype_alnum("123"));
+var_dump(ctype_alnum("abc"));
+var_dump(ctype_alnum("abc 123"));
+var_dump(ctype_alnum("abc!"));
+var_dump(ctype_alnum(""));
+
+var_dump(ctype_alpha("abcDEF"));
+var_dump(ctype_alpha("abc"));
+var_dump(ctype_alpha("ABC"));
+var_dump(ctype_alpha("abc123"));
+var_dump(ctype_alpha("abc!"));
+var_dump(ctype_alpha(""));
+
+var_dump(ctype_digit("123456"));
+var_dump(ctype_digit("0"));
+var_dump(ctype_digit("123abc"));
+var_dump(ctype_digit("12.34"));
+var_dump(ctype_digit(""));
+var_dump(ctype_digit(" "));
+
+var_dump(ctype_lower("abcdef"));
+var_dump(ctype_lower("abc"));
+var_dump(ctype_lower("abc123"));
+var_dump(ctype_lower("abcDef"));
+var_dump(ctype_lower("ABC"));
+var_dump(ctype_lower(""));
+
+var_dump(ctype_upper("ABCDEF"));
+var_dump(ctype_upper("ABC"));
+var_dump(ctype_upper("ABC123"));
+var_dump(ctype_upper("abc"));
+var_dump(ctype_upper("AbC"));
+var_dump(ctype_upper(""));
+
+var_dump(ctype_space(" "));
+var_dump(ctype_space("\t"));
+var_dump(ctype_space("\n"));
+var_dump(ctype_space(" \n\t"));
+var_dump(ctype_space("abc"));
+var_dump(ctype_space(""));
+
+var_dump(ctype_xdigit("0123456789abcdef"));
+var_dump(ctype_xdigit("ABCDEF"));
+var_dump(ctype_xdigit("123G"));
+var_dump(ctype_xdigit("xyz"));
+var_dump(ctype_xdigit(""));
+var_dump(ctype_xdigit("0FfA"));
+
+var_dump(ctype_cntrl("\n"));
+var_dump(ctype_cntrl("\r\t"));
+var_dump(ctype_cntrl("\0"));
+var_dump(ctype_cntrl("abc"));
+var_dump(ctype_cntrl(" "));
+var_dump(ctype_cntrl(""));
+
+var_dump(ctype_graph("abc123!@#"));
+var_dump(ctype_graph("!@#"));
+var_dump(ctype_graph("abc\n"));
+var_dump(ctype_graph(" "));
+var_dump(ctype_graph(""));
+var_dump(ctype_graph("abc"));
+
+var_dump(ctype_print("abc123!@# "));
+var_dump(ctype_print(" "));
+var_dump(ctype_print("abc\n"));
+var_dump(ctype_print("\t"));
+var_dump(ctype_print(""));
+var_dump(ctype_print("abc!"));
+
+var_dump(ctype_punct("!@#$%^&*()"));
+var_dump(ctype_punct(".,;:!?"));
+var_dump(ctype_punct("abc!"));
+var_dump(ctype_punct(" "));
+var_dump(ctype_punct(""));
+var_dump(ctype_punct("!@#abc"));