diff --git a/phper/src/values.rs b/phper/src/values.rs
index 810eb95..2861c91 100644
--- a/phper/src/values.rs
+++ b/phper/src/values.rs
@@ -238,22 +238,12 @@ pub struct ZVal {
 
 /// Conversion from immutable [`ZVal`].
 pub trait FromZVal<'a>: Sized {
-    /// Converts from `ZVal`, return `None` when type mismatch.
-    fn as_(val: &'a ZVal) -> Option<Self> {
-        Self::expect(val).ok()
-    }
-
     /// Converts from `ZVal`, return [`ExpectTypeError`] when type mismatch.
     fn expect(val: &'a ZVal) -> crate::Result<Self>;
 }
 
 /// Conversion from mutable [`ZVal`].
 pub trait FromZValMut<'a>: Sized {
-    /// Converts from mutable `ZVal`, return `None` when type mismatch.
-    fn as_(val: &'a mut ZVal) -> Option<Self> {
-        Self::expect(val).ok()
-    }
-
     /// Converts from mutable `ZVal`, return [`ExpectTypeError`] when type
     /// mismatch.
     fn expect(val: &'a mut ZVal) -> crate::Result<Self>;
@@ -445,14 +435,6 @@ impl ZVal {
         t.into()
     }
 
-    /// Converts to target type by [`FromZVal`].
-    pub fn as_type<'a, T>(&'a self) -> Option<T>
-    where
-        T: FromZVal<'a>,
-    {
-        T::as_(self)
-    }
-
     /// Converts to target type by [`FromZVal`], otherwise returns
     /// [`ExpectTypeError`].
     pub fn expect_type<'a, T>(&'a self) -> crate::Result<T>
@@ -462,14 +444,6 @@ impl ZVal {
         T::expect(self)
     }
 
-    /// Converts to target mutable type by [`FromZValMut`].
-    pub fn as_mut_type<'a, T>(&'a mut self) -> Option<T>
-    where
-        T: FromZValMut<'a>,
-    {
-        T::as_(self)
-    }
-
     /// Converts to target mutable type by [`FromZValMut`], otherwise returns
     /// [`ExpectTypeError`].
     pub fn expect_mut_type<'a, T>(&'a mut self) -> crate::Result<T>
@@ -615,6 +589,24 @@ impl ZVal {
         self.inner_expect_z_str().map(|x| &*x)
     }
 
+    /// Converts to bytes if `ZVal` is string, otherwise returns
+    /// [`ExpectTypeError`].
+    pub fn expect_bytes(&self) -> crate::Result<&[u8]> {
+        self.expect_z_str().map(ZStr::to_bytes)
+    }
+
+    /// Converts to str if `ZVal` is string and valid UTF-8, otherwise returns
+    /// error.
+    pub fn expect_str(&self) -> crate::Result<&str> {
+        Ok(self.expect_z_str()?.to_str()?)
+    }
+
+    /// Converts to CStr if `ZVal` is string and contains a valid trailing nul,
+    /// otherwise returns error.
+    pub fn expect_c_str(&self) -> crate::Result<&CStr> {
+        Ok(self.expect_z_str()?.to_c_str()?)
+    }
+
     /// Converts to mutable string if `ZVal` is string.
     pub fn as_mut_z_str(&mut self) -> Option<&mut ZStr> {
         self.expect_mut_z_str().ok()
@@ -854,6 +846,24 @@ impl<'a> FromZVal<'a> for bool {
     }
 }
 
+impl<'a> FromZVal<'a> for &'a ZVal {
+    fn expect(val: &'a ZVal) -> crate::Result<Self> {
+        Ok(val)
+    }
+}
+
+impl<'a> FromZValMut<'a> for &'a ZVal {
+    fn expect(val: &'a mut ZVal) -> crate::Result<Self> {
+        Ok(val)
+    }
+}
+
+impl<'a> FromZValMut<'a> for &'a mut ZVal {
+    fn expect(val: &'a mut ZVal) -> crate::Result<Self> {
+        Ok(val)
+    }
+}
+
 impl<'a> FromZVal<'a> for i64 {
     fn expect(val: &'a ZVal) -> crate::Result<Self> {
         val.expect_long()
@@ -884,6 +894,42 @@ impl<'a> FromZVal<'a> for &'a ZStr {
     }
 }
 
+impl<'a> FromZVal<'a> for &'a [u8] {
+    fn expect(val: &'a ZVal) -> crate::Result<Self> {
+        val.expect_bytes()
+    }
+}
+
+impl<'a> FromZValMut<'a> for &'a [u8] {
+    fn expect(val: &'a mut ZVal) -> crate::Result<Self> {
+        val.expect_mut_z_str().map(|s| s.to_bytes())
+    }
+}
+
+impl<'a> FromZVal<'a> for &'a str {
+    fn expect(val: &'a ZVal) -> crate::Result<Self> {
+        val.expect_str()
+    }
+}
+
+impl<'a> FromZValMut<'a> for &'a str {
+    fn expect(val: &'a mut ZVal) -> crate::Result<Self> {
+        Ok(val.expect_mut_z_str()?.to_str()?)
+    }
+}
+
+impl<'a> FromZVal<'a> for &'a CStr {
+    fn expect(val: &'a ZVal) -> crate::Result<Self> {
+        val.expect_c_str()
+    }
+}
+
+impl<'a> FromZValMut<'a> for &'a CStr {
+    fn expect(val: &'a mut ZVal) -> crate::Result<Self> {
+        Ok(val.expect_mut_z_str()?.to_c_str()?)
+    }
+}
+
 impl<'a> FromZValMut<'a> for &'a mut ZStr {
     fn expect(val: &'a mut ZVal) -> crate::Result<Self> {
         val.expect_mut_z_str()
diff --git a/tests/integration/src/values.rs b/tests/integration/src/values.rs
index 164a79e..c4699a6 100644
--- a/tests/integration/src/values.rs
+++ b/tests/integration/src/values.rs
@@ -190,22 +190,37 @@ fn integration_values_as(_: &mut [ZVal]) -> Result<(), Infallible> {
 
     {
         let val = ZVal::default();
-        assert_eq!(val.as_type::<()>(), Some(()));
+        assert_eq!(val.expect_type::<()>().ok(), Some(()));
         assert!(val.expect_type::<()>().is_ok());
         assert!(val.expect_type::<bool>().is_err());
     }
 
     {
         let val = ZVal::from(true);
-        assert_eq!(val.as_type::<bool>(), Some(true));
-        assert_eq!(val.as_type::<i64>(), None);
+        assert_eq!(val.expect_type::<bool>().ok(), Some(true));
+        assert_eq!(val.expect_type::<i64>().ok(), None);
         assert!(val.expect_type::<i64>().is_err());
     }
 
     {
         let mut val = ZVal::from(100i64);
-        assert_eq!(val.as_type::<i64>(), Some(100));
-        if let Some(l) = val.as_mut_type::<&mut i64>() {
+        let borrowed = val.expect_type::<&ZVal>().unwrap();
+        assert_eq!(borrowed.expect_long().unwrap(), 100);
+        let borrowed_from_mut = val.expect_mut_type::<&ZVal>().unwrap();
+        assert_eq!(borrowed_from_mut.expect_long().unwrap(), 100);
+
+        {
+            let borrowed_mut = val.expect_mut_type::<&mut ZVal>().unwrap();
+            *borrowed_mut.expect_mut_long().unwrap() += 1;
+        }
+
+        assert_eq!(val.expect_long().unwrap(), 101);
+    }
+
+    {
+        let mut val = ZVal::from(100i64);
+        assert_eq!(val.expect_type::<i64>().ok(), Some(100));
+        if let Ok(l) = val.expect_mut_type::<&mut i64>() {
             *l += 100;
         }
         assert_eq!(val.expect_type::<i64>().unwrap(), 200);
@@ -214,8 +229,8 @@ fn integration_values_as(_: &mut [ZVal]) -> Result<(), Infallible> {
 
     {
         let mut val = ZVal::from(100f64);
-        assert_eq!(val.as_type::<f64>(), Some(100.));
-        if let Some(d) = val.as_mut_type::<&mut f64>() {
+        assert_eq!(val.expect_type::<f64>().ok(), Some(100.));
+        if let Ok(d) = val.expect_mut_type::<&mut f64>() {
             *d += 100.;
         }
         assert_eq!(val.expect_type::<f64>().unwrap(), 200.);
@@ -225,7 +240,9 @@ fn integration_values_as(_: &mut [ZVal]) -> Result<(), Infallible> {
     {
         let val = ZVal::from("foo");
         assert_eq!(
-            val.as_type::<&phper::strings::ZStr>().unwrap().to_bytes(),
+            val.expect_type::<&phper::strings::ZStr>()
+                .unwrap()
+                .to_bytes(),
             b"foo"
         );
         assert!(val.expect_type::<&phper::arrays::ZArr>().is_err());