pub fn try_from_name(name: &str) -> Result<Self> {
        let mut callable = Zval::new();
        callable.set_string(name, false)?;

        Self::new_owned(callable)
    }
Attempts to create a new [`ZendCallable`] from a function name. Returns
a result containing the callable if the function existed and was
callable.

# Parameters

* `name` - Name of the callable function.

# Errors

Returns an error if the function does not exist or is not callable.

# Example

```no_run
use ext_php_rs::types::ZendCallable;

let strpos = ZendCallable::try_from_name("strpos").unwrap();
let result = strpos.try_call(vec![&"hello", &"e"]).unwrap();
assert_eq!(result.long(), Some(1));
```
src/types/callable.rs