PHP file content echo replace by text and positioning it somewhere in HTML page

Question

I have a PHP script in which I control LEDs over wifi on Raspberry.

    $fileName = __DIR__.'/txt/led2.txt';

        if (!file_exists($fileName) || (file_get_contents($fileName) !== '1' && file_get_contents($fileName) !== '0')) {
            file_put_contents($fileName, '1');
        }

        if (isset($_GET['on4']) && file_get_contents($fileName) === '1') {
            shell_exec("/usr/local/bin/gpio -g write 15 1");
            file_put_contents($fileName, '0');
        }

        else if (isset($_GET['on4']) && file_get_contents($fileName) === '0') {
            shell_exec("/usr/local/bin/gpio -g write 15 0");
            file_put_contents($fileName, '1');
        }

Basically If I press button, script will replace variable in file, when it is on, variable in file = 0 and when it is off, its equals to 1.

I need to show the current status of the LEDs on my web UI. Is it posible? Now I only know if the echo shows 1 or 0, could not it be replaced by some picture or text?

Answer 1

Add an echo statement that displays an image that depends on the state of the LED.

You can also simplify the code by noticing all the repetition and using a variable

$fileName = __DIR__.'/txt/led2.txt';

if (file_exists($fileName)) {
    $current_state = file_get_contents($fileName);
    if ($current_state != "0" && $current_state != "1") {
        file_put_contents($fileName, '1');
        $current_state = 1;
    }
} else {
    $current_state = 1;
    file_put_contents($fileName, $current_state);
}

if (isset($_GET['on4'])) {
    shell_exec("/usr/local/bin/gpio -g write 15 $current_state");
    $current_state = 1 - $current_state;
    file_put_contents($fileName, $current_state);
}

echo $current_state == 1 ? '<img src="images/ledOff.png">' :  '<img src="images/ledOn.png">';