String

When a String type is encountered, the zend string content is copied to/from a Rust String object. If the zval does not contain a string, it will attempt to read a double from the zval and convert it into a String object.

Internally, PHP stores strings in zend_string objects, which is a refcounted C struct containing the string length with the content of the string appended to the end of the struct based on how long the string is. Since the string is NUL-terminated, you cannot have any NUL bytes in your string, and an error will be thrown if one is encountered while converting a String to a zval.

Rust example

#![cfg_attr(windows, feature(abi_vectorcall))]
extern crate ext_php_rs;
use ext_php_rs::prelude::*;
#[php_function]
pub fn str_example(input: String) -> String {
    format!("Hello {}", input)
}
fn main() {}

PHP example

<?php

var_dump(str_example("World")); // string(11) "Hello World"
var_dump(str_example(5)); // string(7) "Hello 5"