php script rerun on saved changes

monitor-run.php

<?php

function monitor ($file)
{
	$last = filemtime($file);

	$command = trim(`which php`);
	$command .= " -f " . $file;
	$command .= ' 2>&1';

	$i = 1;
	$out = 0;

	$clear = implode('', array_map('chr', array(27, 91, 72, 27, 91, 50, 74)));
	$line = str_repeat('-', exec('tput cols'));
	echo $clear;

	while (true) {
		$cols = exec('tput cols');
		echo date('r') . ' running for #' . $i++ . ': ' . $command ."\n";
		echo $line;

		passthru($command, $out);

		echo "\n$line";

		# success
		echo "Exit status: $out\n";

		# loop and wait til file changes so we can re-run it
		while (true) {
			clearstatcache();
			$new = filemtime($file);

			if ($new != $last) {
				break;
			}

			# sleep for 1 secs if previous run died, or else .4 seconds
			usleep($out != 0 ? 1000000 : 400000);
		}

		$last = $new;
		echo $clear;
	}
}

monitor($argv[1]);