diff --git a/NEWS b/NEWS
index cb68d41c3332..54bebd00464d 100644
--- a/NEWS
+++ b/NEWS
@@ -144,6 +144,8 @@ PHP                                                                        NEWS
     (Nicolas Grekas)
   . Fixed bug GH-24373 (serialize() called from a destructor during var_hash
     destruction reuses the outer var_hash). (David Carlier)
+  . Fixed bug GH-24552 (Case-insensitive substr_compare(), ksort() and
+    krsort() are still locale-dependent). (Lazizbek Ergashev, Jon Surrell)
 
 - Streams:
   . Fixed bug GH-24508 (HTTP wrapper leaks the dechunk filter when header
diff --git a/ext/standard/array.c b/ext/standard/array.c
index 8454e9616c02..82c3f0a7aa6e 100644
--- a/ext/standard/array.c
+++ b/ext/standard/array.c
@@ -185,7 +185,7 @@ static zend_always_inline int php_array_key_compare_string_case_unstable_i(Bucke
 		s2 = zend_print_long_to_buf(buf2 + sizeof(buf2) - 1, s->h);
 		l2 = buf2 + sizeof(buf2) - 1 - s2;
 	}
-	return zend_binary_strcasecmp_l(s1, l1, s2, l2);
+	return zend_binary_strcasecmp(s1, l1, s2, l2);
 }
 /* }}} */
 
diff --git a/ext/standard/string.c b/ext/standard/string.c
index 9f8e45af3299..8b0f8ec572bb 100644
--- a/ext/standard/string.c
+++ b/ext/standard/string.c
@@ -6352,7 +6352,7 @@ PHP_FUNCTION(substr_compare)
 	if (!cs) {
 		RETURN_LONG(zend_binary_strncmp(ZSTR_VAL(s1) + offset, (ZSTR_LEN(s1) - offset), ZSTR_VAL(s2), ZSTR_LEN(s2), cmp_len));
 	} else {
-		RETURN_LONG(zend_binary_strncasecmp_l(ZSTR_VAL(s1) + offset, (ZSTR_LEN(s1) - offset), ZSTR_VAL(s2), ZSTR_LEN(s2), cmp_len));
+		RETURN_LONG(zend_binary_strncasecmp(ZSTR_VAL(s1) + offset, (ZSTR_LEN(s1) - offset), ZSTR_VAL(s2), ZSTR_LEN(s2), cmp_len));
 	}
 }
 /* }}} */
diff --git a/ext/standard/tests/strings/gh24552.phpt b/ext/standard/tests/strings/gh24552.phpt
new file mode 100644
index 000000000000..97d350e2096e
--- /dev/null
+++ b/ext/standard/tests/strings/gh24552.phpt
@@ -0,0 +1,38 @@
+--TEST--
+GH-24552 (Case-insensitive substr_compare, ksort, krsort are still locale-dependent)
+--SKIPIF--
+<?php
+if (setlocale(LC_CTYPE, "de_DE.ISO8859-1", "de_DE") === false) {
+    die("skip de_DE locale not available");
+}
+?>
+--FILE--
+<?php
+setlocale(LC_CTYPE, "de_DE.ISO8859-1", "de_DE");
+
+var_dump(substr_compare("\xC4", "\xE4", 0, 1, true));
+var_dump(strncasecmp("\xC4", "\xE4", 1));
+
+$keys = ["\xE4" => 0, "\xC4" => 0];
+ksort($keys, SORT_STRING | SORT_FLAG_CASE);
+var_dump(array_map('bin2hex', array_keys($keys)));
+
+$keys = ["\xC4" => 0, "\xE4" => 0];
+krsort($keys, SORT_STRING | SORT_FLAG_CASE);
+var_dump(array_map('bin2hex', array_keys($keys)));
+?>
+--EXPECT--
+int(-32)
+int(-32)
+array(2) {
+  [0]=>
+  string(2) "c4"
+  [1]=>
+  string(2) "e4"
+}
+array(2) {
+  [0]=>
+  string(2) "e4"
+  [1]=>
+  string(2) "c4"
+}