How to Send MIDI Messages from PHP via Serial Port – A Step-by-Step Guide

As music technology advances, more devices support the MIDI (Musical Instrument Digital Interface) protocol, which enables communication between instruments from different manufacturers. This article introduces how to communicate with MIDI devices using PHP and provides a complete code example.

The MIDI protocol is a digital communication standard that defines the data format and transmission method for musical equipment. A MIDI message consists of three bytes: a status byte that indicates the message type, followed by two data bytes that carry the actual values. For instance, the status byte 0x90 represents a “Note On” message, and a data byte such as 0x40 can indicate velocity (volume).

To interact with a MIDI device from PHP, you can use a serial‑communication extension. The following code demonstrates opening a serial port, configuring it for the MIDI baud rate (31250), sending a simple Note On message, and then closing the port.

<?php
// Open serial communication
$serial = new PhpSerial();

$serial->deviceSet("/dev/ttyUSB0");
$serial->confBaudRate(31250);
$serial->confParity("none");
$serial->confCharacterLength(8);
$serial->confStopBits(1);
$serial->confFlowControl("none");

$serial->deviceOpen();

// Send MIDI message
$statusByte = 0x90; // Note On
$dataByte1  = 60;   // Middle C
$dataByte2  = 127;  // Maximum velocity

$message = pack("C*", $statusByte, $dataByte1, $dataByte2);
$serial->sendMessage($message);

// Close serial communication
$serial->deviceClose();
?>

In the example, a PhpSerial object is instantiated, then the serial device (e.g., /dev/ttyUSB0) and MIDI‑specific parameters are set: a baud rate of 31250, no parity, 8‑bit characters, one stop bit, and no flow control. After calling deviceOpen(), the script builds a three‑byte MIDI packet with pack("C*", ...) and transmits it using sendMessage(). Finally, deviceClose() releases the port.

While this snippet shows a basic “Note On” transmission, it can be expanded. You might wrap the logic in functions to send different message types (e.g., Note Off, Control Change), implement a listener to receive incoming MIDI data, and add error‑handling or exception mechanisms to improve stability in real‑world applications.

In summary, by leveraging PHP’s serial communication capabilities, developers can directly send MIDI commands to musical hardware. The provided example offers a starting point for building more sophisticated PHP‑based music‑tech projects and encourages further experimentation with MIDI integration.