What causes "Argument $path must not be an empty string" in Intervention/image?

Pass null (not '') when you want to save back to the original file path

Intervention/image · error · Intervention\Image\Exceptions\InvalidArgumentException

Argument $path must not be an empty string

Error message

Argument $path must not be an empty string

What it means

Image::save() treats an empty string as an explicitly invalid path, distinct from null. Passing null means 'reuse the original file path from the image origin', while '' is almost certainly a bug — typically an unset variable or missing user input coerced to a string. The check runs before any encoding work, so nothing is written when it throws.

Solutions

Pass null (not '') when you want to save back to the original file path
Default missing user input to null: $request->input('path') returns null when absent — avoid ?? '' overrides
Validate: if ($path === '') { abort / use fallback path } before calling save()
Initialize path variables to null rather than '' so the origin-fallback logic can work

Example fix

// before
$path = $request->input('path') ?? '';
$image->save($path); // throws when input missing

// after
$path = $request->input('path'); // null when absent
$image->save($path); // falls back to original file path

Defensive patterns

Strategy: validation

Validate before calling

$path = $request->input('path'); // null, not ''
if ($path === '') {
    $path = null; // let save() fall back to the origin path
}
$image->save($path);

Type guard

function isSaveablePath(?string $path): bool
{
    return $path === null || $path !== '';
}

Try / catch

try {
    $image->save($path);
} catch (InvalidArgumentException $e) {
    // empty-string bug in caller: fix the caller, do not retry
}

Prevention

Default path variables to null, never ''
Avoid ?? '' overrides on request/config lookups feeding save()
Add a save-path unit assertion in controller tests

When it happens

Trigger: $image->save('') — e.g. save($request->input('path')), save($config['output'] ?? '') or save($filename) where $filename was initialized to '' and never set. Note save(null) is valid when the image has a file origin.

Common situations: Form/config values defaulting to empty string instead of null, path variables reset in loops, or string interpolation producing '' — common in Laravel controller code feeding request input straight to save().

Related errors

AI-assisted analysis of Intervention/image@5598b9e397 (2026-08-23). Data as JSON: /api/errors/8f3bbd9696667063. Report an issue: GitHub.

Appendix: source

Thrown at src/Image.php:309

        return $this->driver()->specializeAnalyzer($analyzer)->analyze($this);
    }

    /**
     * {@inheritdoc}
     *
     * @see ImageInterface::save()
     *
     * @throws InvalidArgumentException
     * @throws EncoderException
     * @throws DirectoryNotFoundException
     * @throws FileNotWritableException
     * @throws StreamException
     * @throws NotSupportedException
     */
    public function save(?string $path = null, mixed ...$options): ImageInterface
    {
        if ($path === '') {
            throw new InvalidArgumentException('Argument $path must not be an empty string');
        }

        if (is_null($path) && is_null($this->origin()->filePath())) {
            throw new EncoderException('Unable to determine path for saving');
        }

        $path = is_null($path) ? $this->origin()->filePath() : $path;

        try {
            // try to determine encoding format by file extension of the path
            $encoded = $this->encode(new FilePathEncoder($path, ...$options));
        } catch (EncoderException) {
            // fallback to encoding format by media type
            $encoded = $this->encode(new MediaTypeEncoder(null, ...$options));
        }

        $encoded->save($path);

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