refactor(function-exists): drop checks for always-present capabilities

function_exists() returns false in PHP when a function is blocked by
disable_functions, when its extension is not compiled in, or when the
PHP version predates it. None of those apply to a native binary.

15 files changed, 59 insertions, 202 deletions

diff --git a/crates/shirabe-class-map-generator/src/php_file_parser.rs b/crates/shirabe-class-map-generator/src/php_file_parser.rs
index b7fb595c..0cb9180f 100644
--- a/crates/shirabe-class-map-generator/src/php_file_parser.rs
+++ b/crates/shirabe-class-map-generator/src/php_file_parser.rs
@@ -2,9 +2,8 @@
 
 use crate::php_file_cleaner::PhpFileCleaner;
 use shirabe_php_shim::{
-    PHP_EOL, RuntimeException, file_exists, file_get_contents, function_exists, is_file,
-    is_readable, ltrim, php_strip_whitespace, preg_match_all, str_replace_array, strrpos, substr,
-    trim,
+    PHP_EOL, RuntimeException, file_exists, file_get_contents, is_file, is_readable, ltrim,
+    php_strip_whitespace, preg_match_all, str_replace_array, strrpos, substr, trim,
 };
 use std::sync::OnceLock;
 
@@ -14,10 +13,6 @@ impl PhpFileParser {
     pub fn find_classes(path: &str) -> anyhow::Result<Vec<String>> {
         let extra_types = Self::get_extra_types();
 
-        if !function_exists("php_strip_whitespace") {
-            return Err(RuntimeException::new("Classmap generation relies on the php_strip_whitespace function, but it has been disabled by the disable_functions directive.".to_string()).into());
-        }
-
         // Use @ here instead of Silencer to actively suppress 'unhelpful' output
         let contents = match php_strip_whitespace(path) {
             Ok(contents) if !contents.is_empty() => contents,
diff --git a/crates/shirabe-symfony-console/src/output/console_output.rs b/crates/shirabe-symfony-console/src/output/console_output.rs
index 4080d688..9c2904db 100644
--- a/crates/shirabe-symfony-console/src/output/console_output.rs
+++ b/crates/shirabe-symfony-console/src/output/console_output.rs
@@ -98,11 +98,7 @@ impl ConsoleOutput {
     /// doesn't properly convert character-encodings between ASCII to EBCDIC.
     fn is_running_os400() -> bool {
         let checks = [
-            if shirabe_php_shim::function_exists("php_uname") {
-                shirabe_php_shim::php_uname("s")
-            } else {
-                String::new()
-            },
+            shirabe_php_shim::php_uname("s"),
             shirabe_php_shim::getenv("OSTYPE")
                 .unwrap_or_default()
                 .to_string_lossy()
diff --git a/crates/shirabe-symfony-console/src/terminal.rs b/crates/shirabe-symfony-console/src/terminal.rs
index 492d8fe2..c7bc82b8 100644
--- a/crates/shirabe-symfony-console/src/terminal.rs
+++ b/crates/shirabe-symfony-console/src/terminal.rs
@@ -62,11 +62,6 @@ impl Terminal {
             return stty;
         }
 
-        // skip check if shell_exec function is disabled
-        if !shirabe_php_shim::function_exists("shell_exec") {
-            return false;
-        }
-
         let result = shirabe_php_shim::shell_exec(&format!(
             "stty 2> {}",
             if cfg!(windows) { "NUL" } else { "/dev/null" }
@@ -195,10 +190,6 @@ impl Terminal {
     }
 
     fn read_from_process(command: &str) -> Option<String> {
-        if !shirabe_php_shim::function_exists("proc_open") {
-            return None;
-        }
-
         // Sparse PHP descriptorspec `[1 => ['pipe', 'w'], 2 => ['pipe', 'w']]`: fd 0 is inherited.
         let descriptorspec = [
             shirabe_php_shim::Descriptor::Inherit,
diff --git a/crates/shirabe-symfony-process/src/process.rs b/crates/shirabe-symfony-process/src/process.rs
index 991bdd08..06e60cab 100644
--- a/crates/shirabe-symfony-process/src/process.rs
+++ b/crates/shirabe-symfony-process/src/process.rs
@@ -213,13 +213,6 @@ impl Process {
         input: PhpMixed,
         timeout: Option<f64>,
     ) -> anyhow::Result<Self> {
-        if !shirabe_php_shim::function_exists("proc_open") {
-            return Err(LogicException::new(
-                "The Process class relies on proc_open, which is not available on your PHP installation.".to_string(),
-            )
-            .into());
-        }
-
         let mut this = Self::empty();
         this.commandline = CommandLine::Array(command);
         this.cwd = cwd;
diff --git a/crates/shirabe/src/cache.rs b/crates/shirabe/src/cache.rs
index edfe584c..a8e4fb26 100644
--- a/crates/shirabe/src/cache.rs
+++ b/crates/shirabe/src/cache.rs
@@ -8,9 +8,9 @@ use crate::util::Silencer;
 use chrono::Utc;
 use shirabe_php_shim::{
     ErrorException, bin2hex, clearstatcache, date_format_to_strftime, dirname, disk_free_space,
-    file_exists, file_get_contents, file_put_contents, filemtime, function_exists, hash_file,
-    is_dir, is_writable, mkdir, php_regex, preg_is_match, preg_match, preg_replace, random_bytes,
-    random_int, rename, time, unlink,
+    file_exists, file_get_contents, file_put_contents, filemtime, hash_file, is_dir, is_writable,
+    mkdir, php_regex, preg_is_match, preg_match, preg_replace, random_bytes, random_int, rename,
+    time, unlink,
 };
 use shirabe_symfony_finder::Finder;
 use std::sync::Mutex;
@@ -195,13 +195,9 @@ impl Cache {
                         // Remove partial file.
                         unlink(&temp_file_name);
 
-                        let free_space = if function_exists("disk_free_space") {
-                            disk_free_space(dirname(&temp_file_name))
-                                .map(|space| space.to_string())
-                                .unwrap_or_default()
-                        } else {
-                            "unknown".to_string()
-                        };
+                        let free_space = disk_free_space(dirname(&temp_file_name))
+                            .map(|space| space.to_string())
+                            .unwrap_or_default();
                         let message = format!(
                             "<warning>Writing {} into cache failed after {} of {} bytes written, only {} bytes of free space available</warning>",
                             temp_file_name,
diff --git a/crates/shirabe/src/console/application.rs b/crates/shirabe/src/console/application.rs
index 54df0b05..d73a1c6b 100644
--- a/crates/shirabe/src/console/application.rs
+++ b/crates/shirabe/src/console/application.rs
@@ -246,7 +246,7 @@ impl Application {
         // avoid overlapping borrows of self (get_composer needs &mut self).
         let disk_hint_msg: Option<String> = (|| -> anyhow::Result<Option<String>> {
             let composer = self.get_composer(false, Some(true), None)?;
-            if let Some(composer) = composer && function_exists("disk_free_space") {
+            if let Some(composer) = composer {
                 let composer = composer.borrow_partial();
                 let config = composer.get_config();
 
@@ -1536,9 +1536,7 @@ impl Application {
             input.borrow_mut().set_interactive(false);
         }
 
-        if shirabe_php_shim::function_exists("putenv") {
-            unsafe { shirabe_php_shim::putenv("SHELL_VERBOSITY", shell_verbosity.to_string()) };
-        }
+        unsafe { shirabe_php_shim::putenv("SHELL_VERBOSITY", shell_verbosity.to_string()) };
         shirabe_php_shim::PHP_ENV
             .lock()
             .unwrap()
@@ -2106,7 +2104,6 @@ impl ApplicationHandle {
         }
 
         let needs_sudo_check = !Platform::is_windows()
-            && function_exists("exec")
             && Platform::get_env("COMPOSER_ALLOW_SUPERUSER").is_none()
             && !Platform::is_docker();
         let mut is_non_allowed_root = false;
@@ -2243,16 +2240,13 @@ impl ApplicationHandle {
         if !is_proxy_command {
             io.write_error3(
                 &format!(
-                    "Running Shirabe {} ({}, based on Composer {}) with PHP {} on {}",
+                    "Running Shirabe {} ({}, based on Composer {}) with PHP {} on {} / {}",
                     composer::SHIRABE_VERSION,
                     composer::SHIRABE_RELEASE_DATE,
                     composer::VERSION,
                     shirabe_php_rpc::get_php_version().version,
-                    (if function_exists("php_uname") {
-                        format!("{} / {}", php_uname("s"), php_uname("r"))
-                    } else {
-                        "Unknown OS".to_string()
-                    }),
+                    php_uname("s"),
+                    php_uname("r"),
                 ),
                 true,
                 io_interface::DEBUG,
@@ -2305,11 +2299,7 @@ impl ApplicationHandle {
 
             // Check system temp folder for usability as it can cause weird runtime issues otherwise
             let tempfile_msg: Option<String> = Silencer::call(|| -> anyhow::Result<Option<String>> {
-                let pid = if function_exists("getmypid") {
-                    format!("{}-", getmypid())
-                } else {
-                    String::new()
-                };
+                let pid = format!("{}-", getmypid());
                 let tempfile = format!(
                     "{}/temp-{}{}",
                     sys_get_temp_dir(),
@@ -2688,14 +2678,12 @@ impl ApplicationHandle {
         output: Option<std::rc::Rc<std::cell::RefCell<dyn OutputInterface>>>,
     ) -> anyhow::Result<i32> {
         let application = &self.0;
-        if shirabe_php_shim::function_exists("putenv") {
-            let (height, width) = {
-                let app = application.borrow();
-                (app.terminal.get_height(), app.terminal.get_width())
-            };
-            unsafe { shirabe_php_shim::putenv("LINES", height.to_string()) };
-            unsafe { shirabe_php_shim::putenv("COLUMNS", width.to_string()) };
-        }
+        let (height, width) = {
+            let app = application.borrow();
+            (app.terminal.get_height(), app.terminal.get_width())
+        };
+        unsafe { shirabe_php_shim::putenv("LINES", height.to_string()) };
+        unsafe { shirabe_php_shim::putenv("COLUMNS", width.to_string()) };
 
         let input: std::rc::Rc<std::cell::RefCell<dyn InputInterface>> = match input {
             None => std::rc::Rc::new(std::cell::RefCell::new(ArgvInput::new(None, None)?)),
diff --git a/crates/shirabe/src/downloader/path_downloader.rs b/crates/shirabe/src/downloader/path_downloader.rs
index 6b3531f4..a96d8db7 100644
--- a/crates/shirabe/src/downloader/path_downloader.rs
+++ b/crates/shirabe/src/downloader/path_downloader.rs
@@ -21,9 +21,7 @@ use crate::util::HttpDownloader;
 use crate::util::Platform;
 use crate::util::ProcessExecutor;
 use indexmap::IndexMap;
-use shirabe_php_shim::{
-    PhpMixed, RuntimeException, file_exists, function_exists, impl_php_class, is_dir, realpath,
-};
+use shirabe_php_shim::{PhpMixed, RuntimeException, file_exists, impl_php_class, is_dir, realpath};
 use shirabe_symfony_filesystem::Filesystem as SymfonyFilesystem;
 
 #[derive(Debug)]
@@ -160,19 +158,6 @@ impl PathDownloader {
             allowed_strategies = vec![Self::STRATEGY_MIRROR];
         }
 
-        // Check we can use symlink() otherwise
-        if !Platform::is_windows()
-            && Self::STRATEGY_SYMLINK == current_strategy
-            && !function_exists("symlink")
-        {
-            if !allowed_strategies.contains(&Self::STRATEGY_MIRROR) {
-                return Err(RuntimeException::new("Your PHP has the symlink() function disabled which does not allow Shirabe to use symlinks and this path repository has symlink:true in its options so copying is not allowed".to_string())
-                .into());
-            }
-            current_strategy = Self::STRATEGY_MIRROR;
-            allowed_strategies = vec![Self::STRATEGY_MIRROR];
-        }
-
         Ok((current_strategy, allowed_strategies))
     }
 
diff --git a/crates/shirabe/src/downloader/zip_downloader.rs b/crates/shirabe/src/downloader/zip_downloader.rs
index 565005d9..a63aca18 100644
--- a/crates/shirabe/src/downloader/zip_downloader.rs
+++ b/crates/shirabe/src/downloader/zip_downloader.rs
@@ -11,9 +11,9 @@ use indexmap::IndexMap;
 use shirabe_php_shim::Catch as _;
 use shirabe_php_shim::{
     CmpOp, ErrorException, PhpMixed, RuntimeException, UnexpectedValueException, ZipArchive,
-    bin2hex, class_exists, file_exists, file_get_contents, filesize, function_exists, hash_file,
-    impl_php_class, is_file, json_encode, php_regex, preg_match, random_int, str_replace, strlen,
-    substr, version_compare,
+    bin2hex, class_exists, file_exists, file_get_contents, filesize, hash_file, impl_php_class,
+    is_file, json_encode, php_regex, preg_match, random_int, str_replace, strlen, substr,
+    version_compare,
 };
 use shirabe_symfony_process::ExecutableFinder;
 use std::sync::Mutex;
@@ -528,11 +528,6 @@ impl crate::downloader::DownloaderInterface for ZipDownloader {
             }
         }
 
-        let proc_open_missing = !function_exists("proc_open");
-        if proc_open_missing {
-            *UNZIP_COMMANDS.lock().unwrap() = Some(vec![]);
-        }
-
         {
             let mut has_zip_archive = HAS_ZIP_ARCHIVE.lock().unwrap();
             if has_zip_archive.is_none() {
@@ -549,17 +544,10 @@ impl crate::downloader::DownloaderInterface for ZipDownloader {
 
         if !has_zip_archive && unzip_commands_empty {
             let ini_message = IniHelper::get_message();
-            let error = if proc_open_missing {
-                format!(
-                    "The zip extension is missing and unzip/7z commands cannot be called as proc_open is disabled, skipping.\n{}",
-                    ini_message
-                )
-            } else {
-                format!(
-                    "The zip extension and unzip/7z commands are both missing, skipping.\n{}",
-                    ini_message
-                )
-            };
+            let error = format!(
+                "The zip extension and unzip/7z commands are both missing, skipping.\n{}",
+                ini_message
+            );
             return Err(RuntimeException::new(error).into());
         }
 
@@ -569,15 +557,9 @@ impl crate::downloader::DownloaderInterface for ZipDownloader {
                 *is_windows_guard = Some(Platform::is_windows());
 
                 if !is_windows_guard.unwrap() && unzip_commands_empty {
-                    if proc_open_missing {
-                        self.inner.io.borrow().write_error("<warning>proc_open is disabled so 'unzip' and '7z' commands cannot be used, zip files are being unpacked using the PHP zip extension.</warning>");
-                        self.inner.io.borrow().write_error("<warning>This may cause invalid reports of corrupted archives. Besides, any UNIX permissions (e.g. executable) defined in the archives will be lost.</warning>");
-                        self.inner.io.borrow().write_error("<warning>Enabling proc_open and installing 'unzip' or '7z' (21.01+) may remediate them.</warning>");
-                    } else {
-                        self.inner.io.borrow().write_error("<warning>As there is no 'unzip' nor '7z' command installed zip files are being unpacked using the PHP zip extension.</warning>");
-                        self.inner.io.borrow().write_error("<warning>This may cause invalid reports of corrupted archives. Besides, any UNIX permissions (e.g. executable) defined in the archives will be lost.</warning>");
-                        self.inner.io.borrow().write_error("<warning>Installing 'unzip' or '7z' (21.01+) may remediate them.</warning>");
-                    }
+                    self.inner.io.borrow().write_error("<warning>As there is no 'unzip' nor '7z' command installed zip files are being unpacked using the PHP zip extension.</warning>");
+                    self.inner.io.borrow().write_error("<warning>This may cause invalid reports of corrupted archives. Besides, any UNIX permissions (e.g. executable) defined in the archives will be lost.</warning>");
+                    self.inner.io.borrow().write_error("<warning>Installing 'unzip' or '7z' (21.01+) may remediate them.</warning>");
                 }
             }
         }
diff --git a/crates/shirabe/src/package/archiver/phar_archiver.rs b/crates/shirabe/src/package/archiver/phar_archiver.rs
index ea04a302..75e5a775 100644
--- a/crates/shirabe/src/package/archiver/phar_archiver.rs
+++ b/crates/shirabe/src/package/archiver/phar_archiver.rs
@@ -7,7 +7,7 @@ use indexmap::IndexMap;
 use shirabe_php_shim::Catch as _;
 use shirabe_php_shim::{
     FilesystemIterator, Phar, PharData, RuntimeException, UnexpectedValueException, bzcompress,
-    file_exists, file_put_contents, function_exists, gzcompress, str_repeat, strrpos, unlink,
+    file_exists, file_put_contents, gzcompress, str_repeat, strrpos, unlink,
 };
 
 fn formats() -> IndexMap<&'static str, i64> {
@@ -108,11 +108,11 @@ impl ArchiverInterface for PharArchiver {
                         ))
                         .into());
                     }
-                    if format == "tar.gz" && function_exists("gzcompress") {
+                    if format == "tar.gz" {
                         let data =
                             gzcompress(&str_repeat("\0", 10240).into_bytes()).unwrap_or_default();
                         file_put_contents(&target, &data);
-                    } else if format == "tar.bz2" && function_exists("bzcompress") {
+                    } else if format == "tar.bz2" {
                         let data =
                             bzcompress(&str_repeat("\0", 10240).into_bytes()).unwrap_or_default();
                         file_put_contents(&target, &data);
diff --git a/crates/shirabe/src/package/locker.rs b/crates/shirabe/src/package/locker.rs
index ec8d86e7..17911c6e 100644
--- a/crates/shirabe/src/package/locker.rs
+++ b/crates/shirabe/src/package/locker.rs
@@ -27,9 +27,8 @@ use indexmap::IndexMap;
 use shirabe_php_shim::Catch as _;
 use shirabe_php_shim::{
     DATE_RFC3339, LogicException, PhpMixed, RuntimeException, array_intersect, array_keys,
-    array_map, array_merge, file_get_contents, filemtime, function_exists, hash, in_array_loose,
-    is_int, ksort, php_regex, preg_is_match, preg_match, realpath, strcmp, strtolower, touch2,
-    trim, usort,
+    array_map, array_merge, file_get_contents, filemtime, hash, in_array_loose, is_int, ksort,
+    php_regex, preg_is_match, preg_match, realpath, strcmp, strtolower, touch2, trim, usort,
 };
 use shirabe_seld_json_lint::ParsingException;
 
@@ -773,10 +772,6 @@ impl Locker {
         &mut self,
         package: PackageInterfaceHandle,
     ) -> anyhow::Result<Option<String>> {
-        if !function_exists("proc_open") {
-            return Ok(None);
-        }
-
         let path = self
             .installation_manager
             .borrow_mut()
diff --git a/crates/shirabe/src/package/version/version_guesser.rs b/crates/shirabe/src/package/version/version_guesser.rs
index 3c47d5b2..38c4f0a3 100644
--- a/crates/shirabe/src/package/version/version_guesser.rs
+++ b/crates/shirabe/src/package/version/version_guesser.rs
@@ -13,9 +13,9 @@ use crate::util::Svn as SvnUtil;
 use crate::util::sync_executor;
 use indexmap::IndexMap;
 use shirabe_php_shim::{
-    PhpMixed, RuntimeException, array_keys, array_map, array_merge, empty, function_exists,
-    implode, is_string, json_encode, php_regex, preg_is_match, preg_match, preg_quote,
-    preg_replace, str_replace, strlen, strnatcasecmp, strpos, substr, trim, usort,
+    PhpMixed, RuntimeException, array_keys, array_map, array_merge, empty, implode, is_string,
+    json_encode, php_regex, preg_is_match, preg_match, preg_quote, preg_replace, str_replace,
+    strlen, strnatcasecmp, strpos, substr, trim, usort,
 };
 
 /// Seam over the parts of [`VersionGuesser`] that consumers depend on, so they can be exercised
@@ -104,10 +104,6 @@ impl VersionGuesser {
             return Ok(None);
         }
 
-        if !function_exists("proc_open") {
-            return Ok(None);
-        }
-
         // bypass version guessing in bash completions as it takes time to create
         // new processes and the root version is usually not that important
         if Platform::is_input_completion_process() {
diff --git a/crates/shirabe/src/util/filesystem.rs b/crates/shirabe/src/util/filesystem.rs
index 41b81b7b..2395d1cd 100644
--- a/crates/shirabe/src/util/filesystem.rs
+++ b/crates/shirabe/src/util/filesystem.rs
@@ -6,11 +6,11 @@ use crate::util::Silencer;
 use shirabe_php_shim::{
     ErrorException, LogicException, PhpMixed, PregMatches, RuntimeException, array_pop, basename,
     chdir, clearstatcache, clearstatcache2, copy, dirname, explode, fclose, feof, file_exists,
-    file_get_contents, file_put_contents, fileatime, filemtime, filesize, fopen, fread,
-    function_exists, fwrite, implode, is_dir, is_file, is_link, is_readable, lstat, mkdir,
-    php_regex, preg_is_match, preg_match, preg_replace, preg_replace_callback, rename, rmdir,
-    rtrim, str_repeat, str_replace, strlen, strpos, strtoupper, strtr, substr, substr_count,
-    symlink, touch, unlink, usleep, var_export,
+    file_get_contents, file_put_contents, fileatime, filemtime, filesize, fopen, fread, fwrite,
+    implode, is_dir, is_file, is_link, is_readable, lstat, mkdir, php_regex, preg_is_match,
+    preg_match, preg_replace, preg_replace_callback, rename, rmdir, rtrim, str_repeat, str_replace,
+    strlen, strpos, strtoupper, strtr, substr, substr_count, symlink, touch, unlink, usleep,
+    var_export,
 };
 use shirabe_symfony_filesystem::exception::IOException;
 use shirabe_symfony_finder::Finder;
@@ -114,9 +114,6 @@ impl Filesystem {
     }
 
     /// Recursively remove a directory
-    ///
-    /// Uses the process component if proc_open is enabled on the PHP
-    /// installation.
     pub fn remove_directory(&mut self, directory: impl AsRef<Path>) -> anyhow::Result<bool> {
         // TODO(bytes):
         // This path is matched against a regex (remove_edge_cases) and passed to an
@@ -129,7 +126,7 @@ impl Filesystem {
                 directory.display()
             ))
         })?;
-        let edge_case_result = self.remove_edge_cases(directory, true)?;
+        let edge_case_result = self.remove_edge_cases(directory)?;
         if let Some(r) = edge_case_result {
             return Ok(r);
         }
@@ -167,13 +164,6 @@ impl Filesystem {
     }
 
     /// Recursively remove a directory asynchronously
-    ///
-    /// Uses the process component if proc_open is enabled on the PHP
-    /// installation.
-    ///
-    /// Takes the shared handle instead of `&mut self`: the Filesystem is borrowed only for the
-    /// synchronous head and tail, never across the subprocess await, so sibling futures can keep
-    /// using the same `Rc<RefCell<Filesystem>>` while the removal runs.
     pub async fn remove_directory_async_via(
         this: &std::rc::Rc<std::cell::RefCell<Filesystem>>,
         directory: &str,
@@ -189,7 +179,7 @@ impl Filesystem {
                 return Ok(result);
             }
 
-            let edge_case_result = fs.remove_edge_cases(directory, true)?;
+            let edge_case_result = fs.remove_edge_cases(directory)?;
             if let Some(r) = edge_case_result {
                 return Ok(r);
             }
@@ -225,11 +215,7 @@ impl Filesystem {
     }
 
     /// Returns null when no edge case was hit. Otherwise a bool whether removal was successful
-    fn remove_edge_cases(
-        &mut self,
-        directory: &str,
-        fallback_to_php: bool,
-    ) -> anyhow::Result<Option<bool>> {
+    fn remove_edge_cases(&mut self, directory: &str) -> anyhow::Result<Option<bool>> {
         if self.is_symlinked_directory(directory) {
             return Ok(Some(self.unlink_symlinked_directory(directory)?));
         }
@@ -251,10 +237,6 @@ impl Filesystem {
             .into());
         }
 
-        if !function_exists("proc_open") && fallback_to_php {
-            return Ok(Some(self.remove_directory_php(directory)?));
-        }
-
         Ok(None)
     }
 
@@ -264,7 +246,7 @@ impl Filesystem {
     /// before directories, creating a single non-recursive loop
     /// to delete files/directories in the correct order.
     pub fn remove_directory_php(&mut self, directory: &str) -> anyhow::Result<bool> {
-        let edge_case_result = self.remove_edge_cases(directory, false)?;
+        let edge_case_result = self.remove_edge_cases(directory)?;
         if let Some(r) = edge_case_result {
             return Ok(r);
         }
@@ -497,10 +479,6 @@ impl Filesystem {
             RuntimeException::new(format!("Path contains invalid UTF-8: {}", target.display()))
         })?;
 
-        if !function_exists("proc_open") {
-            return self.copy_then_remove(source, target);
-        }
-
         if Platform::is_windows() {
             // Try to copy & delete - this is a workaround for random "Access denied" errors.
             let mut output = String::new();
@@ -884,10 +862,6 @@ impl Filesystem {
 
     /// Creates a relative symlink from $link to $target
     pub fn relative_symlink(&self, target: &str, link: &str) -> bool {
-        if !function_exists("symlink") {
-            return false;
-        }
-
         let cwd = Platform::get_cwd(false).unwrap_or_default();
 
         let relative_path = self.find_shortest_path(link, target, false, false);
diff --git a/crates/shirabe/src/util/http_downloader.rs b/crates/shirabe/src/util/http_downloader.rs
index 36ccb712..8d34dcdf 100644
--- a/crates/shirabe/src/util/http_downloader.rs
+++ b/crates/shirabe/src/util/http_downloader.rs
@@ -19,8 +19,8 @@ use indexmap::IndexMap;
 use shirabe_php_shim::Catch as _;
 use shirabe_php_shim::{
     InvalidArgumentException, LogicException, PhpMixed, array_replace_recursive, extension_loaded,
-    file_get_contents, function_exists, implode, is_numeric, php_regex, preg_is_match, preg_match,
-    preg_replace, rawurldecode, stream_context_create, stripos, strpos, substr, ucfirst,
+    file_get_contents, implode, is_numeric, php_regex, preg_is_match, preg_match, preg_replace,
+    rawurldecode, stream_context_create, stripos, strpos, substr, ucfirst,
 };
 use shirabe_semver::constraint::SimpleConstraint;
 
@@ -505,8 +505,6 @@ impl HttpDownloader {
     /// @internal
     pub fn is_curl_enabled() -> bool {
         extension_loaded("curl")
-            && function_exists("curl_multi_exec")
-            && function_exists("curl_multi_init")
     }
 
     /// For testing only. Builds an HttpDownloader whose request methods are fully
diff --git a/crates/shirabe/src/util/platform.rs b/crates/shirabe/src/util/platform.rs
index ccee2953..c40f3ec5 100644
--- a/crates/shirabe/src/util/platform.rs
+++ b/crates/shirabe/src/util/platform.rs
@@ -4,8 +4,8 @@ use crate::util::ProcessExecutor;
 use crate::util::Silencer;
 use shirabe_php_shim::{
     PHP_ENV, PHP_SERVER, PhpMixed, PhpResource, PregMatches, RuntimeException, defined,
-    file_exists, file_get_contents, fstat, function_exists, getcwd, getenv, ini_get, is_readable,
-    mb_strlen, php_os_family, php_regex, posix_geteuid, posix_getpwuid, posix_getuid, posix_isatty,
+    file_exists, file_get_contents, function_exists, getcwd, getenv, ini_get, is_readable,
+    mb_strlen, php_os_family, php_regex, posix_geteuid, posix_getpwuid, posix_getuid,
     preg_is_match, preg_replace_callback, putenv, putenv_clear, realpath, stream_isatty, stripos,
     strlen, strtoupper, substr, usleep,
 };
@@ -244,9 +244,7 @@ impl Platform {
         let mut use_mb_string = USE_MB_STRING.lock().unwrap();
         if use_mb_string.is_none() {
             *use_mb_string = Some(
-                function_exists("mb_strlen")
-                    && ini_get("mbstring.func_overload")
-                        .is_some_and(|s| PhpMixed::String(s).to_bool()),
+                ini_get("mbstring.func_overload").is_some_and(|s| PhpMixed::String(s).to_bool()),
             );
         }
 
@@ -270,29 +268,7 @@ impl Platform {
             return true;
         }
 
-        // modern cross-platform function, includes the fstat
-        // fallback so if it is present we trust it
-        if function_exists("stream_isatty") {
-            return stream_isatty(fd);
-        }
-
-        // only trusting this if it is positive, otherwise prefer fstat fallback
-        if function_exists("posix_isatty") && posix_isatty(fd.clone()) {
-            return true;
-        }
-
-        let stat = Silencer::call(|| Ok(fstat(&fd)));
-        let stat = match stat {
-            Ok(s) => s,
-            Err(_) => return false,
-        };
-        let stat = match stat {
-            Some(stat) => stat,
-            None => return false,
-        };
-
-        // Check if formatted mode is S_IFCHR
-        0o020000 == (stat.mode & 0o170000)
+        stream_isatty(fd)
     }
 
     /// Whether the current command is for bash completion
diff --git a/crates/shirabe/src/util/stream_context_factory.rs b/crates/shirabe/src/util/stream_context_factory.rs
index dea964ec..bce35832 100644
--- a/crates/shirabe/src/util/stream_context_factory.rs
+++ b/crates/shirabe/src/util/stream_context_factory.rs
@@ -9,8 +9,8 @@ use crate::util::http::ProxyManager;
 use indexmap::IndexMap;
 use shirabe_ca_bundle::CaBundle;
 use shirabe_php_shim::{
-    PhpMixed, array_replace_recursive, extension_loaded, function_exists, php_uname,
-    stream_context_create, stripos, uasort,
+    PhpMixed, array_replace_recursive, extension_loaded, php_uname, stream_context_create, stripos,
+    uasort,
 };
 
 pub struct StreamContextFactory;
@@ -180,16 +180,8 @@ impl StreamContextFactory {
             let user_agent = format!(
                 "User-Agent: Composer/{} ({os}; {release}; {php_version}; {http_version}{platform}{ci})",
                 composer::get_version(),
-                os = if function_exists("php_uname") {
-                    php_uname("s")
-                } else {
-                    "Unknown".to_string()
-                },
-                release = if function_exists("php_uname") {
-                    php_uname("r")
-                } else {
-                    "Unknown".to_string()
-                },
+                os = php_uname("s"),
+                release = php_uname("r"),
                 php_version = php_version,
                 http_version = http_version,
                 platform = platform_php_version