diff --git a/src/Symfony/Component/Routing/Loader/AnnotationClassLoader.php b/src/Symfony/Component/Routing/Loader/AnnotationClassLoader.php
index 6abca6ac71..7fb66a6124 100644
--- a/src/Symfony/Component/Routing/Loader/AnnotationClassLoader.php
+++ b/src/Symfony/Component/Routing/Loader/AnnotationClassLoader.php
@@ -153,14 +153,14 @@ abstract class AnnotationClassLoader implements LoaderInterface
             $name = $this->getDefaultRouteName($class, $method);
         }
 
-        $defaults = array_merge($globals['defaults'], $annot->getDefaults());
+        $defaults = array_replace($globals['defaults'], $annot->getDefaults());
         foreach ($method->getParameters() as $param) {
             if ($param->isOptional()) {
                 $defaults[$param->getName()] = $param->getDefaultValue();
             }
         }
-        $requirements = array_merge($globals['requirements'], $annot->getRequirements());
-        $options = array_merge($globals['options'], $annot->getOptions());
+        $requirements = array_replace($globals['requirements'], $annot->getRequirements());
+        $options = array_replace($globals['options'], $annot->getOptions());
 
         $hostnamePattern = $annot->getHostnamePattern();
         if (null === $hostnamePattern) {
diff --git a/src/Symfony/Component/Routing/Matcher/Dumper/PhpMatcherDumper.php b/src/Symfony/Component/Routing/Matcher/Dumper/PhpMatcherDumper.php
index 18c1f9ce96..fb147bced5 100644
--- a/src/Symfony/Component/Routing/Matcher/Dumper/PhpMatcherDumper.php
+++ b/src/Symfony/Component/Routing/Matcher/Dumper/PhpMatcherDumper.php
@@ -37,7 +37,7 @@ class PhpMatcherDumper extends MatcherDumper
      */
     public function dump(array $options = array())
     {
-        $options = array_merge(array(
+        $options = array_replace(array(
             'class'      => 'ProjectUrlMatcher',
             'base_class' => 'Symfony\\Component\\Routing\\Matcher\\UrlMatcher',
         ), $options);
@@ -296,35 +296,29 @@ EOF;
         // optimize parameters array
         if (($matches || $hostnameMatches) && $route->getDefaults()) {
             $vars = array();
-            if ($matches) {
-                $vars[] = '$matches';
-            }
             if ($hostnameMatches) {
                 $vars[] = '$hostnameMatches';
             }
-            if (count($vars) > 1) {
-                $matchesExpr = 'array_merge(' . implode(', ', array_reverse($vars)) . ')';
-            } else {
-                $matchesExpr = current($vars);
+            if ($matches) {
+                $vars[] = '$matches';
             }
+            $vars[] = "array('_route' => '$name')";
 
-            $code .= sprintf("            return array_merge(\$this->mergeDefaults(%s, %s), array('_route' => '%s'));\n"
-                , $matchesExpr, str_replace("\n", '', var_export($route->getDefaults(), true)), $name);
+            $code .= sprintf("            return \$this->mergeDefaults(array_replace(%s), %s);\n"
+                , implode(', ', $vars), str_replace("\n", '', var_export($route->getDefaults(), true)));
 
         } elseif ($matches || $hostnameMatches) {
 
             if (!$matches) {
                 $code .= "            \$matches = \$hostnameMatches;\n";
-            } else {
-                if ($hostnameMatches) {
-                    $code .= "            \$matches = array_merge(\$hostnameMatches, \$matches);\n";
-                }
+            } elseif ($hostnameMatches) {
+                $code .= "            \$matches = array_replace(\$hostnameMatches, \$matches);\n";
             }
 
             $code .= sprintf("            \$matches['_route'] = '%s';\n\n", $name);
             $code .= "            return \$matches;\n";
         } elseif ($route->getDefaults()) {
-            $code .= sprintf("            return %s;\n", str_replace("\n", '', var_export(array_merge($route->getDefaults(), array('_route' => $name)), true)));
+            $code .= sprintf("            return %s;\n", str_replace("\n", '', var_export(array_replace($route->getDefaults(), array('_route' => $name)), true)));
         } else {
             $code .= sprintf("            return array('_route' => '%s');\n", $name);
         }
diff --git a/src/Symfony/Component/Routing/Matcher/UrlMatcher.php b/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
index 26812edb43..2afe0f738e 100644
--- a/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
+++ b/src/Symfony/Component/Routing/Matcher/UrlMatcher.php
@@ -117,8 +117,8 @@ class UrlMatcher implements UrlMatcherInterface
             if (!preg_match($compiledRoute->getRegex(), $pathinfo, $matches)) {
                 continue;
             }
-            $hostnameMatches = array();
 
+            $hostnameMatches = array();
             if ($compiledRoute->getHostnameRegex() && !preg_match($compiledRoute->getHostnameRegex(), $this->context->getHost(), $hostnameMatches)) {
                 continue;
             }
@@ -147,7 +147,7 @@ class UrlMatcher implements UrlMatcherInterface
                 continue;
             }
 
-            return array_merge($this->mergeDefaults(array_merge($matches, $hostnameMatches), $route->getDefaults()), array('_route' => $name));
+            return $this->mergeDefaults(array_replace($matches, $hostnameMatches, array('_route' => $name)), $route->getDefaults());
         }
     }
 
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher1.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher1.php
index dec8ba4a40..98d3cce44e 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher1.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher1.php
@@ -27,7 +27,7 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
 
         // foo
         if (0 === strpos($pathinfo, '/foo') && preg_match('#^/foo/(?<bar>baz|symfony)$#s', $pathinfo, $matches)) {
-            return array_merge($this->mergeDefaults($matches, array (  'def' => 'test',)), array('_route' => 'foo'));
+            return $this->mergeDefaults(array_replace($matches, array('_route' => 'foo')), array (  'def' => 'test',));
         }
 
         if (0 === strpos($pathinfo, '/bar')) {
@@ -177,7 +177,7 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
         if (0 === strpos($pathinfo, '/multi')) {
             // helloWorld
             if (0 === strpos($pathinfo, '/multi/hello') && preg_match('#^/multi/hello(?:/(?<who>[^/]++))?$#s', $pathinfo, $matches)) {
-                return array_merge($this->mergeDefaults($matches, array (  'who' => 'World!',)), array('_route' => 'helloWorld'));
+                return $this->mergeDefaults(array_replace($matches, array('_route' => 'helloWorld')), array (  'who' => 'World!',));
             }
 
             // overridden2
@@ -277,12 +277,12 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
 
                 // route12
                 if ($pathinfo === '/route12') {
-                    return array_merge($this->mergeDefaults($hostnameMatches, array (  'var1' => 'val',)), array('_route' => 'route12'));
+                    return $this->mergeDefaults(array_replace($hostnameMatches, array('_route' => 'route12')), array (  'var1' => 'val',));
                 }
 
                 // route13
                 if (0 === strpos($pathinfo, '/route13') && preg_match('#^/route13/(?<name>[^/]++)$#s', $pathinfo, $matches)) {
-                    $matches = array_merge($hostnameMatches, $matches);
+                    $matches = array_replace($hostnameMatches, $matches);
                     $matches['_route'] = 'route13';
 
                     return $matches;
@@ -290,7 +290,7 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
 
                 // route14
                 if (0 === strpos($pathinfo, '/route14') && preg_match('#^/route14/(?<name>[^/]++)$#s', $pathinfo, $matches)) {
-                    return array_merge($this->mergeDefaults(array_merge($hostnameMatches, $matches), array (  'var1' => 'val',)), array('_route' => 'route14'));
+                    return $this->mergeDefaults(array_replace($hostnameMatches, $matches, array('_route' => 'route14')), array (  'var1' => 'val',));
                 }
 
             }
@@ -310,7 +310,7 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Matcher\UrlMatcher
         if (0 === strpos($pathinfo, '/route1')) {
             // route16
             if (0 === strpos($pathinfo, '/route16') && preg_match('#^/route16/(?<name>[^/]++)$#s', $pathinfo, $matches)) {
-                return array_merge($this->mergeDefaults($matches, array (  'var1' => 'val',)), array('_route' => 'route16'));
+                return $this->mergeDefaults(array_replace($matches, array('_route' => 'route16')), array (  'var1' => 'val',));
             }
 
             // route17
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher2.php b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher2.php
index 607b53fb1d..f4de7eb1b2 100644
--- a/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher2.php
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/dumper/url_matcher2.php
@@ -27,7 +27,7 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
 
         // foo
         if (0 === strpos($pathinfo, '/foo') && preg_match('#^/foo/(?<bar>baz|symfony)$#s', $pathinfo, $matches)) {
-            return array_merge($this->mergeDefaults($matches, array (  'def' => 'test',)), array('_route' => 'foo'));
+            return $this->mergeDefaults(array_replace($matches, array('_route' => 'foo')), array (  'def' => 'test',));
         }
 
         if (0 === strpos($pathinfo, '/bar')) {
@@ -185,7 +185,7 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
         if (0 === strpos($pathinfo, '/multi')) {
             // helloWorld
             if (0 === strpos($pathinfo, '/multi/hello') && preg_match('#^/multi/hello(?:/(?<who>[^/]++))?$#s', $pathinfo, $matches)) {
-                return array_merge($this->mergeDefaults($matches, array (  'who' => 'World!',)), array('_route' => 'helloWorld'));
+                return $this->mergeDefaults(array_replace($matches, array('_route' => 'helloWorld')), array (  'who' => 'World!',));
             }
 
             // overridden2
@@ -289,12 +289,12 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
 
                 // route12
                 if ($pathinfo === '/route12') {
-                    return array_merge($this->mergeDefaults($hostnameMatches, array (  'var1' => 'val',)), array('_route' => 'route12'));
+                    return $this->mergeDefaults(array_replace($hostnameMatches, array('_route' => 'route12')), array (  'var1' => 'val',));
                 }
 
                 // route13
                 if (0 === strpos($pathinfo, '/route13') && preg_match('#^/route13/(?<name>[^/]++)$#s', $pathinfo, $matches)) {
-                    $matches = array_merge($hostnameMatches, $matches);
+                    $matches = array_replace($hostnameMatches, $matches);
                     $matches['_route'] = 'route13';
 
                     return $matches;
@@ -302,7 +302,7 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
 
                 // route14
                 if (0 === strpos($pathinfo, '/route14') && preg_match('#^/route14/(?<name>[^/]++)$#s', $pathinfo, $matches)) {
-                    return array_merge($this->mergeDefaults(array_merge($hostnameMatches, $matches), array (  'var1' => 'val',)), array('_route' => 'route14'));
+                    return $this->mergeDefaults(array_replace($hostnameMatches, $matches, array('_route' => 'route14')), array (  'var1' => 'val',));
                 }
 
             }
@@ -322,7 +322,7 @@ class ProjectUrlMatcher extends Symfony\Component\Routing\Tests\Fixtures\Redirec
         if (0 === strpos($pathinfo, '/route1')) {
             // route16
             if (0 === strpos($pathinfo, '/route16') && preg_match('#^/route16/(?<name>[^/]++)$#s', $pathinfo, $matches)) {
-                return array_merge($this->mergeDefaults($matches, array (  'var1' => 'val',)), array('_route' => 'route16'));
+                return $this->mergeDefaults(array_replace($matches, array('_route' => 'route16')), array (  'var1' => 'val',));
             }
 
             // route17