Architecture

derafu/escpos wraps mike42/escpos-php instead of implementing the ESC/POS protocol itself — but that library is treated as a replaceable implementation detail, not part of this package’s contract. Nothing in the public API accepts or returns a Mike42\Escpos\* type or constant; see Vocabulary and Printing Images for the two places that leak would normally happen (command values, and image types) and how they are closed.

Why this matters

If a consumer’s code imports Mike42\Escpos\* directly to call this package, upgrading mike42/escpos-php to a new major version can break that consumer’s code too — even though they never touched the underlying library’s version themselves. Isolating it behind this package’s own API means a breaking change in the underlying library only needs to be absorbed in one place: here.

The seam: PrinterInterface

Derafu\Escpos\Contract\PrinterInterface defines every operation EscposPrinter needs from a backend: text(), feed(), selectPrintMode(), setJustification(), barcode(), pdf417(), image(), cut(), pulse(), getOutput(), close().

Derafu\Escpos\Adapter\Mike42Printer is the only class in this package allowed to use Mike42\Escpos\*, and it is the default implementation of PrinterInterface. EscposPrinter is a thin facade: it owns option resolution, the sprintf()/line-break convenience of print()/println(), special character handling, and the end() workflow (finish, optionally cut and pulse) — and delegates everything else to whichever PrinterInterface it was given.

use Derafu\Escpos\Contract\PrinterInterface;
use Derafu\Escpos\EscposPrinter;

// Normally you never need this — omitting the second argument builds the
// default Mike42Printer from your options array.
$printer = new EscposPrinter($options, $customPrinterImplementation);

That second constructor argument is the extension point: a different backend (or a test double) can be swapped in without changing EscposPrinter’s public API, or any code that already depends on PrinterInterface instead of the concrete class.

Exceptions

Every exception this package throws implements Derafu\Escpos\Exception\EscposExceptionInterface, so you can catch anything it raises without needing to know the specific class:

None of these extend a Mike42\Escpos\* exception, for the same reason described above.