Fix GH-15824 mb_detect_encoding() invalid "UTF8"

I fixed from strcasecmp to strncasecmp.
However, strncasecmp is specify size to #3 parameter.
Hence, Add check strlen to mime and aliases.

Author: youkidearitai

ext/mbstring/libmbfl/mbfl/mbfl_encoding.c

@@ -332,6 +332,10 @@ const mbfl_encoding *mbfl_name2encoding_ex(const char *name, size_t name_len)
 	}
 #endif
 
+	if (name_len == 0) {
+		return NULL;
+	}
+
 	/* Use perfect hash lookup for name */
 	if (name_len <= NAME_HASH_MAX_NAME_LENGTH && name_len >= NAME_HASH_MIN_NAME_LENGTH) {
 		unsigned int key = mbfl_name2encoding_perfect_hash(name, name_len);
@@ -349,7 +353,7 @@ const mbfl_encoding *mbfl_name2encoding_ex(const char *name, size_t name_len)
 	/* search MIME charset name */
 	for (encoding = mbfl_encoding_ptr_list; *encoding; encoding++) {
 		if ((*encoding)->mime_name) {
-			if (strcasecmp((*encoding)->mime_name, name) == 0) {
+			if (strcasecmp((*encoding)->mime_name, name) == 0 && strlen((*encoding)->mime_name) == name_len) {
 				return *encoding;
 			}
 		}
@@ -359,7 +363,7 @@ const mbfl_encoding *mbfl_name2encoding_ex(const char *name, size_t name_len)
 	for (encoding = mbfl_encoding_ptr_list; *encoding; encoding++) {
 		if ((*encoding)->aliases) {
 			for (const char **alias = (*encoding)->aliases; *alias; alias++) {
-				if (strcasecmp(*alias, name) == 0) {
+				if (strncasecmp(name, *alias, name_len) == 0 && strlen(*alias) == name_len) {
 					return *encoding;
 				}
 			}

ext/mbstring/tests/gh15824.phpt

@@ -0,0 +1,10 @@
+--TEST--
+GH-15824 (ValueError: mb_detect_encoding(): Argument #2 ($encodings) contains invalid encoding "UTF8")
+--EXTENSIONS--
+mbstring
+--FILE--
+<?php
+echo mb_detect_encoding('abc', 'UTF8, ASCII');
+?>
+--EXPECT--
+UTF-8