diff --git a/binding/php/ReadMe.md b/binding/php/ReadMe.md
index 0c42ea9..c00a073 100644
--- a/binding/php/ReadMe.md
+++ b/binding/php/ReadMe.md
@@ -2,30 +2,57 @@
 
 # 使用方式
 
-第三方 composer 地址: 
+第三方 composer 地址 (请自行确认仓库对 IPv6 的支持): 
 1. [https://github.com/zoujingli/ip2region](https://github.com/zoujingli/ip2region)
 2. [https://github.com/chinayin/ip2region-core-php](https://github.com/chinayin/ip2region-core-php)
 
+
+### 关于 IPv4 和 IPv6
+该 xdb 查询客户端实现同时支持对 IPv4 和 IPv6 的查询，使用方式如下：
+```php
+use \ip2region\xdb\{IPv4, IPv6};
+
+// 如果是 IPv4: 设置 xdb 路径为 v4 的 xdb 文件，IP版本指定为 IPv4
+$dbFile  = "../../data/ip2region_v4.xdb";  // 或者你的 ipv4 xdb 的路径
+$version = IPv4::default();
+
+// 如果是 IPv6: 设置 xdb 路径为 v6 的 xdb 文件，IP版本指定为 IPv6
+$dbFile  = "../../data/ip2region_v6.xdb";  // 或者你的 ipv6 xdb 路径
+$version = IPv6::default();
+
+// dbPath 指定的 xdb 的 IP 版本必须和 version 指定的一致，不然查询执行的时候会报错
+// 备注：以下演示直接使用 $dbFile 和 $version 变量
+```
+
 ### 完全基于文件的查询
 ```php
-$dbFile = "ip2region.xdb file path";
+// require or autoload the xdb\Searcher
+require 'xdb\Searcher.php';
+use \ip2region\xdb\Util;
+use \ip2region\xdb\Searcher;
+
+// 1, 使用上述的 $version 和 $dbFile 创建 Searcher 对象
 try {
-    $searcher = XdbSearcher::newWithFileOnly($dbFile);
+    $searcher = Searcher::newWithFileOnly($version, $dbFile);
 } catch (Exception $e) {
-    printf("failed to create searcher with '%s': %s\n", $dbFile, $e);
+    printf("failed to create searcher with '%s': %s\n", $dbFile, $e->getMessage());
     return;
 }
 
-$ip = '1.2.3.4';
-$sTime = XdbSearcher::now();
-$region = $searcher->search($ip);
-if ($region === null) {
-    // something is wrong
-    printf("failed search(%s)\n", $ip);
-    return;
+// 2, 查询，IPv4 或者 IPv6 的地址都支持
+try {
+    $ip = '1.2.3.4';
+    // $ip = "2001:4:112:ffff:ffff:ffff:ffff:ffff"; // IPv6
+    $sTime  = Util::now();
+    $region = $searcher->search($ip);
+    $costMs = Util::now() - $sTime;
+    printf("{region: %s, took: %.5f ms}\n", $region, $costMs);
+} catch (Exception $e) {
+    printf("failed to search(%s): %s", $ip, $e->getMessage());
 }
 
-printf("{region: %s, took: %.5f ms}\n", $region, XdbSearcher::now() - $sTime);
+// 3，关闭资源
+$searcher->close();
 
 // 备注：并发使用，每个线程或者协程需要创建一个独立的 searcher 对象。
 ```
@@ -34,62 +61,84 @@ printf("{region: %s, took: %.5f ms}\n", $region, XdbSearcher::now() - $sTime);
 
 如果你的 php 母环境支持，可以预先加载 vectorIndex 缓存，然后做成全局变量，每次创建 Searcher 的时候使用全局的 vectorIndex，可以减少一次固定的 IO 操作从而加速查询，减少 io 压力。 
 ```php
-// 1、从 dbPath 加载 VectorIndex 缓存，把下述的 vIndex 变量缓存到内存里面。
-$vIndex = XdbSearcher::loadVectorIndexFromFile($dbPath);
+// require or autoload the xdb\Searcher
+require 'xdb\Searcher.php';
+use \ip2region\xdb\Util;
+use \ip2region\xdb\Searcher;
+
+
+// 1、从 $dbFile 加载 VectorIndex 缓存，把下述的 vIndex 变量缓存到内存里面。
+$vIndex = Util::loadVectorIndexFromFile($dbFile);
 if ($vIndex === null) {
-    printf("failed to load vector index from '%s'\n", $dbPath);
+    printf("failed to load vector index from '%s'\n", $dbFile);
     return;
 }
 
 // 2、使用全局的 vIndex 创建带 VectorIndex 缓存的查询对象。
 try {
-    $searcher = XdbSearcher::newWithVectorIndex($dbFile, $vIndex);
+    $searcher = Searcher::newWithVectorIndex($version, $dbFile, $vIndex);
 } catch (Exception $e) {
-    printf("failed to create vectorIndex cached searcher with '%s': %s\n", $dbFile, $e);
+    printf("failed to create vectorIndex searcher with '%s': %s\n", $dbFile, $e->getMessage());
     return;
 }
 
-// 3、查询
-$sTime = XdbSearcher::now();
-$region = $searcher->search('1.2.3.4');
-if ($region === null) {
-    printf("failed search(1.2.3.4)\n");
-    return;
+// 3、查询，IPv4 或者 IPv6 都支持
+try {
+    $ip = '1.2.3.4';
+    // $ip = "2001:4:112:ffff:ffff:ffff:ffff:ffff"; // IPv6
+    $sTime  = Util::now();
+    $region = $searcher->search($ip);
+    $costMs = Util::now() - $sTime;
+    printf("{region: %s, took: %.5f ms}\n", $region, $costMs);
+} catch (Exception $e) {
+    printf("failed to search(%s): %s", $ip, $e->getMessage());
 }
 
-printf("{region: %s, took: %.5f ms}\n", $region, XdbSearcher::now() - $sTime);
+// 4, 关闭资源
+$searcher->close();
 
-// 备注：并发使用，每个线程或者协程需要创建一个独立的 searcher 对象，但是都共享统一的只读 vectorIndex。
+// 备注：并发使用，每个线程或者协程需要创建一个独立的 searcher 对象，但是都共享统一的只读全局 vectorIndex。。
 ```
 
 ### 缓存整个 `xdb` 数据
 
 如果你的 PHP 母环境支持，可以预先加载整个 `xdb` 的数据到内存，这样可以实现完全基于内存的查询，类似之前的 memory search 查询。
 ```php
-// 1、从 dbPath 加载整个 xdb 到内存。
-$cBuff = XdbSearcher::loadContentFromFile($dbPath);
+// require or autoload the xdb\Searcher
+require 'xdb\Searcher.php';
+use \ip2region\xdb\Util;
+use \ip2region\xdb\Searcher;
+
+// 1、从 $dbFile 加载整个 xdb 到内存。
+$cBuff = Util::loadContentFromFile($dbFile);
 if ($cBuff === null) {
-    printf("failed to load content buffer from '%s'\n", $dbPath);
+    printf("failed to load content buffer from '%s'\n", $dbFile);
     return;
 }
 
 // 2、使用全局的 cBuff 创建带完全基于内存的查询对象。
 try {
-    $searcher = XdbSearcher::newWithBuffer($cBuff);
+    $searcher = Searcher::newWithBuffer($version, $cBuff);
 } catch (Exception $e) {
-    printf("failed to create buffer cached searcher: %s\n", $dbFile, $e);
+    printf("failed to create buffer cached searcher: %s\n", $dbFile, $e->getMessage());
     return;
 }
 
-// 3、查询
-$sTime = XdbSearcher::now();
-$region = $searcher->search('1.2.3.4');
-if ($region === null) {
-    printf("failed search(1.2.3.4)\n");
-    return;
+// 3、查询，IPv4 或者 IPv6 都支持
+try {
+    $ip = '1.2.3.4';
+    // $ip = "2001:4:112:ffff:ffff:ffff:ffff:ffff"; // IPv6
+    $sTime  = Util::now();
+    $region = $searcher->search($ip);
+    $costMs = Util::now() - $sTime;
+    printf("{region: %s, took: %.5f ms}\n", $region, $costMs);
+} catch (Exception $e) {
+    printf("failed to search(%s): %s", $ip, $e->getMessage());
 }
 
-printf("{region: %s, took: %.5f ms}\n", $region, XdbSearcher::now() - $sTime);
+// 4，关闭资源
+// 该 searcher 对象可以安全的用于并发，等整个服务都关闭的时候再关闭 searcher
+// $searcher->close();
 
 // 备注：并发使用，用整个 xdb 缓存创建的 searcher 对象可以安全用于并发。
 ```
@@ -98,21 +147,33 @@ printf("{region: %s, took: %.5f ms}\n", $region, XdbSearcher::now() - $sTime);
 
 通过 `search_test.php` 脚本来进行查询测试：
 ```bash
-➜  php git:(v2.0_xdb) ✗ php ./search_test.php
-php ./search_test.php [command options]
-options:
+➜  php git:(fr_php_ipv6) ✗ php search_test.php 
+php search_test.php [command options]
+options: 
  --db string             ip2region binary xdb file path
  --cache-policy string   cache policy: file/vectorIndex/content
 ```
 
-例如：使用默认的 data/ip2region.xdb 进行查询测试：
+例如：使用默认的 data/ip2region_v4.xdb 进行 IPv4 的查询测试：
 ```bash
-➜  php git:(v2.0_xdb) ✗ php ./search_test.php --db=../../data/ip2region.xdb --cache-policy=vectorIndex
-ip2region xdb searcher test program, cachePolicy: vectorIndex
+➜  php git:(fr_php_ipv6) ✗ php search_test.php --db=../../data/ip2region_v4.xdb
+ip2region xdb searcher test program
+source xdb file: ../../data/ip2region_v4.xdb (IPv4, vectorIndex)
 type 'quit' to exit
-ip2region>> 1.2.3.4
-{region: 美国|0|华盛顿|0|谷歌, ioCount: 7, took: 0.04492 ms}
-ip2region>> 
+ip2region>> 120.229.45.2
+{region: 中国|广东省|深圳市|移动, ioCount: 3, took: 0.02783 ms}
+```
+
+例如：使用默认的 data/ip2region_v6.xdb 进行 IPv6 的查询测试：
+```bash
+➜  php git:(fr_php_ipv6) ✗ php search_test.php --db=../../data/ip2region_v6.xdb
+ip2region xdb searcher test program
+source xdb file: ../../data/ip2region_v6.xdb (IPv6, vectorIndex)
+type 'quit' to exit
+ip2region>> ::
+{region: |||, ioCount: 2, took: 0.06982 ms}
+ip2region>> 2604:bc80:8001:11a4:ffff:ffff:ffff:ffff
+{region: 中国|广东省|深圳市|数据中心, ioCount: 13, took: 0.19409 ms}
 ```
 
 输入 ip 即可进行查询测试。也可以分别设置 `cache-policy` 为 file/vectorIndex/content 来测试三种不同缓存实现的效率。
@@ -121,18 +182,22 @@ ip2region>>
 
 通过 `bench_test.php` 脚本来进行自动 bench 测试，一方面确保 `xdb` 文件没有错误，另一方面通过大量的查询测试平均查询性能：
 ```bash
-➜  php git:(v2.0_xdb) ✗ php ./bench_test.php
-php ./bench_test.php [command options]
-options:
+➜  php git:(fr_php_ipv6) ✗ php bench_test.php
+php bench_test.php [command options]
+options: 
  --db string             ip2region binary xdb file path
  --src string            source ip text file path
  --cache-policy string   cache policy: file/vectorIndex/content
 ```
 
-例如：通过默认的 data/ip2region.xdb 和 data/ip.merge.txt 来进行 bench 测试：
+例如：通过默认的 data/ip2region_v4.xdb 和 data/ipv4_source.txt 文件进行 IPv4 的 bench 测试：
 ```bash
-➜  php git:(v2.0_xdb) ✗ php ./bench_test.php --db=../../data/ip2region.xdb --src=../../data/ip.merge.txt --cache-policy=vectorIndex
-Bench finished, {cachePolicy: vectorIndex, total: 3417955, took: 15s, cost: 0.005 ms/op}
+php bench_test.php --db=../../data/ip2region_v4.xdb --src=../../data/ipv4_source.txt
+```
+
+例如：通过默认的 data/ip2region_v6.xdb 和 data/ipv6_source.txt 文件进行 IPv6 的 bench 测试：
+```bash
+php bench_test.php --db=../../data/ip2region_v6.xdb --src=../../data/ipv6_source.txt
 ```
 
 可以通过设置 `cache-policy` 参数来分别测试 file/vectorIndex/content 三种不同的缓存实现的的性能。
diff --git a/binding/php/batch_test.php b/binding/php/batch_test.php
index 14ecd37..85e61bc 100644
--- a/binding/php/batch_test.php
+++ b/binding/php/batch_test.php
@@ -6,7 +6,11 @@
 // @Author Lion <chenxin619315@gmail.com>
 // @Date   2022/06/22
 
-require dirname(__FILE__) . '/XdbSearcher.class.php';
+require dirname(__FILE__) . '/xdb/Searcher.class.php';
+
+use \ip2region\xdb\Util;
+use \ip2region\xdb\{IPv4, IPv6};
+use \ip2region\xdb\Searcher;
 
 function printHelp($argv) {
     printf("php %s [command options]\n", $argv[0]);
@@ -60,39 +64,60 @@ if (strlen($dbFile) < 1 || strlen($srcFile) < 1) {
 }
 
 // printf("debug: dbFile: %s, cachePolicy: %s\n", $dbFile, $cachePolicy);
+$handle = fopen($dbFile, 'r');
+if ($handle === false) {
+    printf("failed to open the xdb file `{$dbFile}`\n");
+    return;
+}
+
+// load header
+$header = Util::loadHeader($handle);
+if ($header == null) {
+    printf("failed to load the header\n");
+    return;
+}
+
+// get the version number from the xdb header
+try {
+    $version = Util::versionFromHeader($header);
+} catch (Exception $e) {
+    printf("failed to detect version from header: {$e->getMessage()}\n");
+    return;
+}
+
 // create the xdb searcher by the cache-policy
 switch ( $cachePolicy ) {
     case 'file':
         try {
-            $searcher = XdbSearcher::newWithFileOnly($dbFile);
+            $searcher = Searcher::newWithFileOnly($version, $dbFile);
         } catch (Exception $e) {
             printf("failed to create searcher with '%s': %s\n", $dbFile, $e);
             return;
         }
         break;
     case 'vectorIndex':
-        $vIndex = XdbSearcher::loadVectorIndexFromFile($dbFile);
+        $vIndex = Util::loadVectorIndex($handle);
         if ($vIndex == null) {
             printf("failed to load vector index from '%s'\n", $dbFile);
             return;
         }
 
         try {
-            $searcher = XdbSearcher::newWithVectorIndex($dbFile, $vIndex);
+            $searcher = Searcher::newWithVectorIndex($version, $dbFile, $vIndex);
         } catch (Exception $e) {
             printf("failed to create vector index cached searcher with '%s': %s\n", $dbFile, $e);
             return;
         }
         break;
     case 'content':
-        $cBuff = XdbSearcher::loadContentFromFile($dbFile);
+        $cBuff = Util::loadContent($handle);
         if ($cBuff == null) {
             printf("failed to load xdb content from '%s'\n", $dbFile);
             return;
         }
 
         try {
-            $searcher = XdbSearcher::newWithBuffer($cBuff);
+            $searcher = Searcher::newWithBuffer($version, $cBuff);
         } catch (Exception $e) {
             printf("failed to create content cached searcher: %s", $e);
             return;
@@ -119,21 +144,18 @@ while (!feof($handle)) {
         continue;
     }
 
-    $ip = XdbSearcher::ip2long($line);
-    if ($ip === null) {
-        printf("invalid ip `%s`\n", $line);
-        return;
+    try {
+        $ipBytes = Util::parseIP($line);
+    } catch (Exception $e) {
+        printf("failed to parse ip `%s`: %s\n", $line, $e->getMessage());
+        continue;
     }
 
     $count++;
-    $region = $searcher->search($ip);
+    $region = $searcher->searchByBytes($ipBytes);
     $ss = explode('|', $region);
-    if (strlen($ss[3]) > 1) {
-        $qx_count++;
-    }
     echo $line, ",", str_replace('|', ',', $region), "\n";
 }
 
 fclose($handle);
-echo "qx_count: {$qx_count}";
 echo "Done, with {$count} IPs\n";
diff --git a/binding/php/bench_test.php b/binding/php/bench_test.php
index 6ea7d4d..75fa111 100644
--- a/binding/php/bench_test.php
+++ b/binding/php/bench_test.php
@@ -64,7 +64,26 @@ if (strlen($dbFile) < 1 || strlen($srcFile) < 1) {
 }
 
 // printf("debug: dbFile: %s, cachePolicy: %s\n", $dbFile, $cachePolicy);
-$version = IPv4::default();
+$handle = fopen($dbFile, 'r');
+if ($handle === false) {
+    printf("failed to open the xdb file `{$dbFile}`\n");
+    return;
+}
+
+// load header
+$header = Util::loadHeader($handle);
+if ($header == null) {
+    printf("failed to load the header\n");
+    return;
+}
+
+// get the version number from the xdb header
+try {
+    $version = Util::versionFromHeader($header);
+} catch (Exception $e) {
+    printf("failed to detect version from header: {$e->getMessage()}\n");
+    return;
+}
 
 // create the xdb searcher by the cache-policy
 switch ( $cachePolicy ) {
@@ -77,7 +96,7 @@ switch ( $cachePolicy ) {
         }
         break;
     case 'vectorIndex':
-        $vIndex = Util::loadVectorIndexFromFile($dbFile);
+        $vIndex = Util::loadVectorIndex($handle);
         if ($vIndex == null) {
             printf("failed to load vector index from '%s'\n", $dbFile);
             return;
@@ -91,7 +110,7 @@ switch ( $cachePolicy ) {
         }
         break;
     case 'content':
-        $cBuff = Util::loadContentFromFile($dbFile);
+        $cBuff = Util::loadContent($handle);
         if ($cBuff == null) {
             printf("failed to load xdb content from '%s'\n", $dbFile);
             return;
@@ -126,6 +145,11 @@ while (!feof($handle)) {
         continue;
     }
 
+    // ignore the comment
+    if ($line[0] == '#') {
+        continue;
+    }
+
     $ps = explode('|', $line, 3);
     if (count($ps) != 3) {
         printf("invalid ip segment line `${line}`\n");
diff --git a/binding/php/search_test.php b/binding/php/search_test.php
index cb62d60..6874af8 100644
--- a/binding/php/search_test.php
+++ b/binding/php/search_test.php
@@ -60,7 +60,26 @@ if (strlen($dbFile) < 1) {
 }
 
 // printf("debug: dbFile: %s, cachePolicy: %s\n", $dbFile, $cachePolicy);
-$version = IPv4::default();
+$handle = fopen($dbFile, 'r');
+if ($handle === false) {
+    printf("failed to open the xdb file `{$dbFile}`\n");
+    return;
+}
+
+// load header
+$header = Util::loadHeader($handle);
+if ($header == null) {
+    printf("failed to load the header\n");
+    return;
+}
+
+// get the version number from the xdb header
+try {
+    $version = Util::versionFromHeader($header);
+} catch (Exception $e) {
+    printf("failed to detect version from header: {$e->getMessage()}\n");
+    return;
+}
 
 // create the xdb searcher by the cache-policy
 switch ( $cachePolicy ) {
@@ -73,7 +92,7 @@ case 'file':
     }
     break;
 case 'vectorIndex':
-    $vIndex = Util::loadVectorIndexFromFile($dbFile);
+    $vIndex = Util::loadVectorIndex($handle);
     if ($vIndex == null) {
         printf("failed to load vector index from '%s'\n", $dbFile);
         return;
@@ -87,7 +106,7 @@ case 'vectorIndex':
     }
     break;
 case 'content':
-    $cBuff = Util::loadContentFromFile($dbFile);
+    $cBuff = Util::loadContent($handle);
     if ($cBuff == null) {
         printf("failed to load xdb content from '%s'\n", $dbFile);
         return;
@@ -105,7 +124,11 @@ default:
     return;
 }
 
-printf("ip2region xdb searcher test program, cachePolicy: ${cachePolicy}\ntype 'quit' to exit\n");
+printf(<<<EOF
+ip2region xdb searcher test program
+source xdb file: {$dbFile} ({$version->name}, ${cachePolicy})
+type 'quit' to exit\n
+EOF);
 while ( true ) {
     echo "ip2region>> ";
     $line = trim(fgets(STDIN));
diff --git a/binding/php/xdb/Searcher.class.php b/binding/php/xdb/Searcher.class.php
index fcc7033..24c7ac5 100644
--- a/binding/php/xdb/Searcher.class.php
+++ b/binding/php/xdb/Searcher.class.php
@@ -42,7 +42,9 @@ class Util {
     // compare two ip bytes (packed string return by parsedIP)
     // returns: -1 if ip1 < ip2, 0 if ip1 == ip2 or 1 if ip1 > ip2
     public static function ipSubCompare($ip1, $buff, $offset) {
-        $r = substr_compare($ip1, $buff, $offset, strlen($ip1));
+        // $r = substr_compare($ip1, $buff, $offset, strlen($ip1));
+        // @Note: substr_compare is not working, use the substr + strcmp instead
+        $r = strcmp($ip1, substr($buff, $offset, strlen($ip1)));
         if ($r < 0) {
             return -1;
         } else if ($r > 0) {
@@ -64,6 +66,48 @@ class Util {
         }
     }
 
+    // version parse
+    public static function versionFromName($ver_name) {
+        $name = strtoupper($ver_name);
+        if ($name == "V4" || $name == "IPv4") {
+            return IPv4::default();
+        } else if ($name == "V6" || $name == "IPv6") {
+            return IPv6::default();
+        } else {
+            throw new Exception("invalid verstion name `{$ver_name}`");
+        }
+    }
+
+    // version parse from header
+    public static function versionFromHeader($header) {
+        // Old structure 2.0 with IPv4 supports ONLY
+        if ($header['version'] == Structure_20) {
+            return IPv4::default();
+        }
+
+        // structure 3.0 after IPv6 supporting
+        if ($header['version'] != Structure_30) {
+            throw new Exception("invalid xdb structure version `{$header['version']}`");
+        }
+
+        if ($header['ipVersion'] == IPv4VersionNo) {
+            return IPv4::default();
+        } else if ($header['ipVersion'] == IPv6VersionNo) {
+            return IPv6::default();
+        } else {
+            throw new Exception("invalid ip version number `{$header['ipVersion']}`");
+        }
+    }
+
+    // binary string chars implode with space
+    public static function bytesToString($buff, $offset, $length) {
+        $sb = [];
+        for ($i = 0; $i < $length; $i++) {
+            $sb[] = ord($buff[$offset+$i]) & 0xFF;
+        }
+        return '['.implode(' ', $sb).']';
+    }
+
     // decode a 4bytes long with Little endian byte order from a byte buffer
     public static function le_getUint32($b, $idx) {
         $val = (ord($b[$idx])) | (ord($b[$idx+1]) << 8)
@@ -203,10 +247,14 @@ class IPv4 {
     public $name;
     public $bytes;
     public $segmentIndexSize;
-
+    
+    private static $C = null;
     public static function default() {
-        // 14 = 4 + 4 + 2 + 4
-        return new self(IPv4VersionNo, 'IPv4', 4, 14);
+        if (self::$C == null) {
+            // 14 = 4 + 4 + 2 + 4
+            self::$C = new self(IPv4VersionNo, 'IPv4', 4, 14);
+        }
+        return self::$C;
     }
 
     public function __construct($id, $name, $bytes, $segmentIndexSize) {
@@ -220,24 +268,23 @@ class IPv4 {
     public function ipSubCompare($ip1, $buff, $offset) {
         // ip1: Little endian byte order encoded long from searcher.
         // ip2: Little endian byte order read from xdb index.
-        // @Note: to compatible with the old Litten endian index encode implementation.
-        $ip2 = (
-            (ord($buff[$offset  ]) << 24) | 
-            (ord($buff[$offset+1]) << 16) | 
-            (ord($buff[$offset+2]) <<  8) | ord($buff[$offset+3])
-        );
-
-        $r = $ip1 - $ip2;
-        if ($r > 0) {
-            return 1;
-        } else if ($r < 0) {
-            return -1;
-        } else {
-            return 0;
+        $len  = strlen($ip1);
+        $eIdx = $offset + $len;
+        for ($i = 0, $j = $eIdx - 1; $i < $len; $i++, $j--) {
+            $i1 = ord($ip1[$i]) & 0xFF;
+            $i2 = ord($buff[$j]) & 0xFF;
+            // printf("i:%d, j:%d, i1:%d, i2:%d\n", $i, $j, $i1, $i2);
+            if ($i1 > $i2) {
+                return 1;
+            } else if ($i1 < $i2) {
+                return -1;
+            }
         }
+
+        return 0;
     }
 
-    public function toString() {
+    public function __toString() {
         return sprintf(
             "{id:%d, name:%s, bytes:%d, segmentIndexSize:%d}", 
             $this->id, $this->name, $this->bytes, $this->segmentIndexSize
@@ -251,9 +298,14 @@ class IPv6 {
     public $bytes;
     public $segmentIndexSize;
 
+    private static $C = null;
     public static function default() {
-        // 38 = 16 + 16 + 2 + 4
-        return new self(IPv6VersionNo, 'IPv6', 16, 38);
+        if (self::$C == null) {
+            // 38 = 16 + 16 + 2 + 4
+            self::$C = new self(IPv6VersionNo, 'IPv6', 16, 38);
+        }
+
+        return self::$C;
     }
 
     public function __construct($id, $name, $bytes, $segmentIndexSize) {
@@ -264,10 +316,11 @@ class IPv6 {
     }
 
     public function ipSubCompare($ip, $buff, $offset) {
+        // return Util::ipCompare($ip, substr($buff, $offset, strlen($ip)));
         return Util::ipSubCompare($ip, $buff, $offset);
     }
 
-    public function toString() {
+    public function __toString() {
         return sprintf(
             "{id:%d, name:%s, bytes:%d, segmentIndexSize:%d}", 
             $this->id, $this->name, $this->bytes, $this->segmentIndexSize
@@ -281,8 +334,7 @@ class Searcher {
     private $version;
 
     // xdb file handle
-    private $handle = null;
-
+    private $handle  = null;
     private $ioCount = 0;
 
     // vector index in binary string.
@@ -406,15 +458,6 @@ class Searcher {
 
         // printf("sPtr: %d, ePtr: %d\n", $sPtr, $ePtr);
         [$bytes, $dBytes] = [strlen($ipBytes), strlen($ipBytes) << 1];
-        if ($bytes == 4) {
-            // encode the IPv4 bytes to an long with Litten endian byte order
-            // to avoid the repeated calcs in the binary search loop.
-            $ipBytes = (
-                (ord($ipBytes[3]) << 24) |
-                (ord($ipBytes[2]) << 24) |
-                (ord($ipBytes[1]) << 24) | (ord($ipBytes[0]))
-            );
-        }
 
         // binary search the segment index to get the region info
         $idxSize = $this->version->segmentIndexSize;
@@ -430,6 +473,11 @@ class Searcher {
                 throw new Exception("failed to read segment index with ptr={$p}");
             }
 
+            // printf("l=%d, h=%d, sip=%s, eip=%s\n", 
+            //     $l, $h,
+            //     Util::ipToString(strrev(substr($buff, 0, 4))),
+            //     Util::ipToString(strrev(substr($buff, 4, 4)))
+            // );
             if ($this->version->ipSubCompare($ipBytes, $buff, 0) < 0) {
                 $h = $m - 1;
             } else if ($this->version->ipSubCompare($ipBytes, $buff, $bytes) > 0) {
diff --git a/binding/php/xdb/util_test.php b/binding/php/xdb/util_test.php
index d5baf9c..1103381 100644
--- a/binding/php/xdb/util_test.php
+++ b/binding/php/xdb/util_test.php
@@ -6,7 +6,7 @@
 // @Author Lion <chenxin619315@gmail.com>
 // @Date   2022/06/22
 
-require dirname(__FILE__) . '/Searcher.class.php';
+require 'Searcher.class.php';
 use \ip2region\xdb\Util;
 use \ip2region\xdb\Searcher;
 use \ip2region\xdb\IPv4;
@@ -20,9 +20,11 @@ if($argc < 2) {
     $func_name = trim($argv[1]);
 }
 
+$basePath = dirname(dirname(dirname(dirname(__FILE__))));
 
 function testLoadHeader() {
-    $header = Util::loadHeaderFromFile('../../data/ip2region_v4.xdb');
+    global $basePath;
+    $header = Util::loadHeaderFromFile("{$basePath}/data/ip2region_v4.xdb");
     if ($header == null) {
         printf("failed to load header from file\n");
         return;
@@ -33,7 +35,8 @@ function testLoadHeader() {
 }
 
 function testLoadVectorIndex() {
-    $vIndex = Util::loadVectorIndexFromFile('../../data/ip2region_v4.xdb');
+    global $basePath;
+    $vIndex = Util::loadVectorIndexFromFile("{$basePath}/data/ip2region_v4.xdb");
     if ($vIndex == null) {
         printf("failed to load vector index from file\n");
         return;
@@ -43,7 +46,8 @@ function testLoadVectorIndex() {
 }
 
 function testLoadContent() {
-    $cBuff = Util::loadContentFromFile('../../data/ip2region_v4.xdb');
+    global $basePath;
+    $cBuff = Util::loadContentFromFile("{$basePath}/data/ip2region_v4.xdb");
     if ($cBuff == null) {
         printf("failed to load content from file\n");
         return;
@@ -87,6 +91,8 @@ function testIPCompare() {
         ["1.0.0.0", "1.0.0.1"],
         ["192.168.1.101", "192.168.1.90"],
         ["219.133.111.87", "114.114.114.114"],
+        ["1.0.4.0", "1.0.1.0"],
+        ["1.0.4.0", "1.0.3.255"],
         ["2000::", "2000:ffff:ffff:ffff:ffff:ffff:ffff:ffff"],
         ["2001:4:112::", "2001:4:112:ffff:ffff:ffff:ffff:ffff"],
         ["ffff::", "2001:4:ffff:ffff:ffff:ffff:ffff:ffff"]
@@ -102,8 +108,8 @@ function testIPCompare() {
 function testAttributes() {
     printf("IPv4VersioNo: %d\n", \ip2region\xdb\IPv4VersionNo);
     printf("IPv6VersioNo: %d\n", \ip2region\xdb\IPv6VersionNo);
-    printf("IPv4 Object: %s\n", IPv4::default()->toString());
-    printf("IPv6 Object: %s\n", IPv6::default()->toString());
+    printf("IPv4 Object: %s\n", IPv4::default());
+    printf("IPv6 Object: %s\n", IPv6::default());
 }