php -m: list loaded PHP extensions (check if an extension is installed)

php -m prints the names of every compiled-in and loaded extension of the PHP command-line interpreter, one per line, under [PHP Modules], followed by [Zend Modules] such as OPcache or Xdebug. Use it to check whether mbstring, intl, pdo_mysql or redis is available before running Composer or an app that needs it. A missing extension usually shows up at run time as Call to undefined function (for example mb_strlen()) or as a Composer platform requirement error.

Listing and checking

The example uses PHP 8.4 compiled to WebAssembly (php-wasm, from the WordPress Playground project), which ships with a fixed set of extensions:

npm init -y >/dev/null
npm install --silent --no-audit --no-fund @php-wasm/node@3.1.56 @php-wasm/universal@3.1.56 >/dev/null 2>&1
cat > php.mjs <<'JS'
// Minimal "php" command: copies *.php files into the virtual file system and runs the CLI
import fs from "node:fs";
import { PHP } from "@php-wasm/universal";
import { loadNodeRuntime } from "@php-wasm/node";
const php = new PHP(await loadNodeRuntime("8.4", { emscriptenOptions: { processId: 1 } }));
php.mkdir("/app");
for (const f of fs.readdirSync(".").filter((f) => f.endsWith(".php"))) php.writeFile(`/app/${f}`, fs.readFileSync(f));
php.chdir("/app");
const r = await php.cli(["php", ...process.argv.slice(2)]);
process.stdout.write(await r.stdoutText);
process.stdout.write(await r.stderrText);
process.exit(await r.exitCode);
JS
node php.mjs -m | head -12
echo "..."
node php.mjs -m | sed -n '/\[Zend Modules\]/,$p'
echo "== is it loaded?"
for ext in mbstring pdo_sqlite intl; do
  if node php.mjs -m | grep -qix "$ext"; then echo "$ext: yes"; else echo "$ext: no"; fi
done
node php.mjs -r 'var_dump(extension_loaded("mbstring"), function_exists("mb_strlen"));'
echo "== details of one extension"
node php.mjs --ri json

[PHP Modules]
bcmath
calendar
Core
ctype
curl
date
dns_polyfill
dom
exif
fileinfo
filter
...
[Zend Modules]
Zend OPcache

== is it loaded?
mbstring: yes
pdo_sqlite: yes
intl: no
bool(true)
bool(true)
== details of one extension

json

json support => enabled

The list is alphabetical within each section and mixes extensions built into the binary (Core, date, standard) with shared ones loaded from php.ini. grep -qix checks for an exact, case-insensitive line, which is what scripts and CI steps need.

Related options

Adding a missing extension

How you install an extension depends on how PHP was installed:

sudo apt install php8.4-intl            # Debian/Ubuntu packages (one package per extension)
sudo dnf install php-intl               # Fedora/RHEL
pecl install redis                      # PECL builds, then add extension=redis to php.ini
docker-php-ext-install intl pdo_mysql   # official php Docker images

On Windows, the DLLs are in the ext folder of the PHP zip; enable them with lines such as extension=intl in php.ini. After installing, php -m must list the extension; if it does not, check that the right php.ini is loaded with php --ini, and test a single run with php -d extension=intl -m.

Pitfalls

• Several PHP versions can be installed side by side (php8.2, php8.4); php -m reports the one that php resolves to on the PATH.
• A broken extension= line prints a startup warning such as Unable to load dynamic library on every run, before the module list.
• Composer checks extensions of the PHP that runs Composer. If CI uses another PHP binary than production, composer install can pass in one and fail in the other.

FAQ