diff --git a/tests/sapi.rs b/tests/sapi.rs
index d74accb89..3e16a67d6 100644
--- a/tests/sapi.rs
+++ b/tests/sapi.rs
@@ -9,7 +9,9 @@
 extern crate ext_php_rs;
 
 use ext_php_rs::builders::SapiBuilder;
-use ext_php_rs::embed::{ext_php_rs_sapi_startup, Embed};
+use ext_php_rs::embed::{
+    ext_php_rs_sapi_per_thread_init, ext_php_rs_sapi_shutdown, ext_php_rs_sapi_startup, Embed,
+};
 use ext_php_rs::ffi::{
     php_module_shutdown, php_module_startup, php_request_shutdown, php_request_startup,
     sapi_shutdown, sapi_startup, ZEND_RESULT_CODE_SUCCESS,
@@ -17,9 +19,15 @@ use ext_php_rs::ffi::{
 use ext_php_rs::prelude::*;
 use ext_php_rs::zend::try_catch_first;
 use std::ffi::c_char;
+use std::sync::Mutex;
 
 static mut LAST_OUTPUT: String = String::new();
 
+// Global mutex to ensure SAPI tests don't run concurrently. PHP does not allow
+// multiple SAPIs to exist at the same time. This prevents the tests from
+// overwriting each other's state.
+static SAPI_TEST_MUTEX: Mutex<()> = Mutex::new(());
+
 extern "C" fn output_tester(str: *const c_char, str_length: usize) -> usize {
     let char = unsafe { std::slice::from_raw_parts(str.cast::<u8>(), str_length) };
     let string = String::from_utf8_lossy(char);
@@ -35,6 +43,8 @@ extern "C" fn output_tester(str: *const c_char, str_length: usize) -> usize {
 
 #[test]
 fn test_sapi() {
+    let _guard = SAPI_TEST_MUTEX.lock().unwrap();
+
     let mut builder = SapiBuilder::new("test", "Test");
     builder = builder.ub_write_function(output_tester);
 
@@ -86,6 +96,10 @@ fn test_sapi() {
     unsafe {
         sapi_shutdown();
     }
+
+    unsafe {
+        ext_php_rs_sapi_shutdown();
+    }
 }
 
 /// Gives you a nice greeting!
@@ -102,3 +116,92 @@ pub fn hello_world(name: String) -> String {
 pub fn module(module: ModuleBuilder) -> ModuleBuilder {
     module.function(wrap_function!(hello_world))
 }
+
+#[test]
+fn test_sapi_multithread() {
+    let _guard = SAPI_TEST_MUTEX.lock().unwrap();
+
+    use std::sync::{Arc, Mutex};
+    use std::thread;
+
+    let mut builder = SapiBuilder::new("test-mt", "Test Multi-threaded");
+    builder = builder.ub_write_function(output_tester);
+
+    let sapi = builder.build().unwrap().into_raw();
+    let module = get_module();
+
+    unsafe {
+        ext_php_rs_sapi_startup();
+    }
+
+    unsafe {
+        sapi_startup(sapi);
+    }
+
+    unsafe {
+        php_module_startup(sapi, module);
+    }
+
+    let results = Arc::new(Mutex::new(Vec::new()));
+    let mut handles = vec![];
+
+    for i in 0..4 {
+        let results = Arc::clone(&results);
+
+        let handle = thread::spawn(move || {
+            unsafe {
+                ext_php_rs_sapi_per_thread_init();
+            }
+
+            let result = unsafe { php_request_startup() };
+            assert_eq!(result, ZEND_RESULT_CODE_SUCCESS);
+
+            let _ = try_catch_first(|| {
+                let eval_result = Embed::eval(&format!("hello_world('thread-{}');", i));
+
+                match eval_result {
+                    Ok(zval) => {
+                        assert!(zval.is_string());
+                        let string = zval.string().unwrap();
+                        let output = string.to_string();
+                        assert_eq!(output, format!("Hello, thread-{}!", i));
+
+                        results.lock().unwrap().push((i, output));
+                    }
+                    Err(_) => panic!("Evaluation failed in thread {}", i),
+                }
+            });
+
+            unsafe {
+                php_request_shutdown(std::ptr::null_mut());
+            }
+        });
+
+        handles.push(handle);
+    }
+
+    for handle in handles {
+        handle.join().expect("Thread panicked");
+    }
+
+    let results = results.lock().unwrap();
+    assert_eq!(results.len(), 4);
+
+    for i in 0..4 {
+        assert!(results
+            .iter()
+            .any(|(idx, output)| { *idx == i && output == &format!("Hello, thread-{}!", i) }));
+    }
+
+    unsafe {
+        php_module_shutdown();
+    }
+
+    unsafe {
+        sapi_shutdown();
+    }
+
+    unsafe {
+        ext_php_rs_sapi_shutdown();
+    }
+}