php rate limiter

RateLimit.php

<?php

class RateLimit
{
	protected $totalTimestamp = 0;
	protected $totalCalls = 0;
	
	protected $timestamp = 0;
	protected $calls = 0;
	protected $limit;
	protected $frequency;
	
	/**
	 *
	 * @param integer $limit Optional calls per frequency
	 * @param integer $frequency Optional frequency in seconds
	 */
	public function __construct($limit = 40, $frequency = 15)
	{
		$this->limit = $limit;
		$this->frequency = $frequency;
		$this->timestamp = microtime(true);
		$this->totalTimestamp = microtime(true);
	}

	/**
	 * Call before every API request
	 */
	public function limit()
	{
		// Increment call counter every request
		$this->calls++;
		$this->totalCalls++;
		// Allow burst of requests until it reaches limit threshold
		if ($this->calls >= $this->limit) {
			$now = microtime(true);
			// Determine time taken
			$duration = $now - $this->timestamp;
			
			// Check if we have requested limit requests too fast
			if ($this->frequency > $duration) {
				// Wait before allowing script to continue sending requests
				$wait = 1000000 * ($this->frequency - ($now - $this->timestamp));
				usleep($wait);
			}
			// Reset current timestamp
			$this->timestamp = microtime(true);
			$this->totalTimestamp = $this->timestamp - $this->totalTimestamp;
			// Reset call counter
			$this->calls = 0;
		}
	}
}

$cl = new RateLimit();

for($i=1; $i<=1000; $i++) {
	echo $i."\n";
	$cl->limit();
}