Simple and customisable command line progress bar in PHP

progressBar.php

<?php

/**
 * Creates a progress bar
 * 
 * @param string $template Template to use, available placeholders are %finished, %unfinished, %percent and %eta
 * @param int $width Width of the progress bar
 * @return callable A function that renders the bar and takes the percent as only argument
 */
function progressBar(
    $template = '[%finished>%unfinished] %percent % - ETA: %eta s',
    $width = 100
)
{
    $symbols = [
        'finished' => '=',
        'unfinished' => ' ',
        'eta' => '?',
    ];

    $template = preg_replace_callback(
        '/%(' . join('|', array_keys($symbols)) . '):(\'|")(.+?)\2/',
        function ($match) use (&$symbols) {
            $symbols[$match[1]] = $match[3];
            return '%' . $match[1];
        },
        $template
    );

    $startTime = null;

    return function ($percent) use ($template, $width, $symbols, &$startTime) {
        if ($startTime === null) {
            if ($percent === 0) {
                $startTime = microtime(true);
            }
            $eta = $symbols['eta'];
        } else {
            $elapsed = microtime(true) - $startTime;
            $eta = (int) ((100 - $percent) * $elapsed / $percent);
        }

        $completed = round($percent * $width / 100);

        $view = str_replace(
            [
                '%finished',
                '%unfinished',
                '%percent',
                '%eta',
            ],
            [
                str_repeat($symbols['finished'], $completed),
                str_repeat($symbols['unfinished'], $width - $completed),
                $percent,
                $eta,
            ],
            $template
        );

        return "\033[" . strlen($view) . "D" . $view; 
    };
}

// usage examples

// default bar
$pb = progressBar();

for ($i = 0; $i <= 100; $i++) {
    echo $pb($i);
    usleep(25000);
}

echo PHP_EOL;

// colors and stuff
$custom = progressBar("\033[42m%finished:' '\033[41m%unfinished\033[0m", 50);

for ($i = 0; $i <= 100; $i++) {
    echo $custom($i);
    usleep(25000);
}

echo PHP_EOL;