Drive an SSD1306 OLED from PHP

private function busInit(): void
{
    gpio_mode($this->scl, GPIO_OUTPUT); gpio_write($this->scl, 1);
    gpio_mode($this->sda, GPIO_OUTPUT); gpio_write($this->sda, 1);
}

/** Clock out one byte, MSB first; the ninth clock is a driven-low fake ACK. */
private function writeByte(int $v): void
{
    $sda = $this->sda;
    $scl = $this->scl;
    for ($i = 0; $i < 8; $i++) {
        gpio_write($sda, ($v >> 7) & 1);
        $v = ($v << 1) & 0xFF;
        gpio_write($scl, 1);
        gpio_write($scl, 0);
    }
    gpio_write($sda, 0);       // ninth clock, SDA held low
    gpio_write($scl, 1);
    gpio_write($scl, 0);
}

PHP_FUNCTION(ssd1306_begin)
{
    zend_long sda, scl, addr = 0x3C;
    ZEND_PARSE_PARAMETERS_START(2, 3)
        Z_PARAM_LONG(sda)
        Z_PARAM_LONG(scl)
        Z_PARAM_OPTIONAL
        Z_PARAM_LONG(addr)
    ZEND_PARSE_PARAMETERS_END();

    s_addr = (uint16_t) addr;

    if (s_bus == NULL) {
        i2c_master_bus_config_t bus_cfg = {
            .i2c_port = -1,                    /* auto-pick a free controller */
            .sda_io_num = (int) sda,
            .scl_io_num = (int) scl,
            .clk_source = I2C_CLK_SRC_DEFAULT,
            .glitch_ignore_cnt = 7,
            .flags = { .enable_internal_pullup = true },
        };
        if (i2c_new_master_bus(&bus_cfg, &s_bus) != ESP_OK) {
            RETURN_FALSE;
        }
    }
    /* ... add device at 400 kHz, then ssd_init_panel() ... */
    RETURN_TRUE;
}

<?php
require __DIR__ . '/SSD1306.php';

const SDA = 7;      // board pin "SDA / GPIO7"
const SCL = 8;      // board pin "SCL / GPIO8"

$oled = null;
$fps  = 0.0;

function setup(): void
{
    global $oled;
    $oled = new SSD1306(SDA, SCL, 0x3C);
    echo $oled->present()
        ? "panel: present (ACK)\n"
        : "panel: no ACK -- check wiring/address; driving blind\n";

    $oled->begin();
    $oled->clear();
    $oled->text(4, 4,  'PHP ' . PHP_MAJOR_VERSION . '.' . PHP_MINOR_VERSION);
    $oled->text(4, 18, 'OLED FPS');
    $oled->flush();
    delay(800);
}

function loop(int $tick): void
{
    global $oled, $fps;
    static $sweep = 0;

    $count = 0;
    $t0 = microtime(true);
    do {                                  // all real drawing, no delay
        $oled->clear();
        $oled->text(0, 18, 'FPS ' . sprintf('%4.1f', $fps));
        $oled->rect($sweep++ % (SSD1306::WIDTH - 14), 27, 14, 5);
        $oled->flush();
        $count++;
        $elapsed = microtime(true) - $t0;
    } while ($elapsed < 0.30);

    $fps = $count / $elapsed;
    printf("draw fps: %5.1f  (%d frames in %d ms)\n",
        $fps, $count, (int) round($elapsed * 1000));
    delay(10);   // yield one tick so the task watchdog stays fed
}

<?php
const SDA = 7;      // board pin "SDA / GPIO7"
const SCL = 8;      // board pin "SCL / GPIO8"

$fps = 0.0;

function setup(): void
{
    if (!function_exists('ssd1306_begin')) {
        echo "ERROR: the ssd1306 extension is not built in -- check firmware/exts/ssd1306/\n";
        return;
    }
    ssd1306_begin(SDA, SCL, 0x3C);
    echo ssd1306_present() ? "panel: present (ACK)\n" : "panel: no ACK -- check wiring\n";

    ssd1306_clear();
    ssd1306_text(4, 4,  'PHP ' . PHP_MAJOR_VERSION . '.' . PHP_MINOR_VERSION);
    ssd1306_text(4, 18, 'C EXT');
    ssd1306_flush();
    delay(800);
}

function loop(int $tick): void
{
    global $fps;
    static $sweep = 0;

    $count = 0;
    $t0 = microtime(true);
    do {                                  // everything in here runs in C
        ssd1306_clear();
        ssd1306_text(0,  0, 'SSD1306 C EXT');
        ssd1306_text(0, 18, 'FPS ' . sprintf('%5.1f', $fps));
        ssd1306_rect($sweep++ % (128 - 14), 27, 14, 5);
        ssd1306_flush();
        $count++;
        $elapsed = microtime(true) - $t0;
    } while ($elapsed < 0.30);

    $fps = $count / $elapsed;
    printf("draw fps: %6.1f  (%d frames in %d ms)\n",
        $fps, $count, (int) round($elapsed * 1000));
    delay(10);   // yield one tick so the task watchdog stays fed
}