followed by a linefeed character (ASCII 10)
		< ozone > followed by a linefeed character (ASCII 10)
		null character (ASCII 0)
		
	*/

	// url of the page with the air quality index data for New York City:
	$url = 'http://airnow.gov/index.cfm?action=airnow.showlocal&cityid=164'; 

    $readParticles = 0;			// flag telling you the next line is the particle value
    $readOzone = 0;				// flag telling you the next line is the ozone value
    $particles = -1;			// the particles value
    $ozone = -1;				// the ozone value
    
	// open the file at the URL for reading:
    $filePath = fopen ($url, "r");
    
    // as long as you haven't reached the end of the file
    while (!feof($filePath))
    {
     	// read one line at a time, and strip all HTML and PHP tags from the line:
     	$line = fgetss($filePath, 4096);

		// if the previous line was the "observed at line" preceding
		// the particle matter reading, then $readParticles = 1 and
		// you should get this line, trim everything but the number,
		// and save the result in $particles:
		if ($readParticles == 1) {
			$particles = trim($line);
			echo "< AQI: $particles>";
			$readParticles = 0;
		}
		
		// if the previous line was the "observed at line" preceding
		// the ozone  reading, then $readOzone = 1 and
		// you should get this line, trim everything but the number,
		// and save the result in $ozone:
		if ($readOzone == 1) {
			$ozone = trim($line);
			//echo "<$ozone>";
			$readOzone = 0;
		}
		
		// if the current line contains the substring "AQI observed at"
		// then the line following it is either the particle reading
		// or the ozone reading:
		if (preg_match('/AQI observed at /', $line)) {
			// if $particles == -1, you haven't gotten
			// a value for it yet, so the next line
			// till be the particle value:
			if ($particles == -1) {
				$readParticles = 1;
			}
			
			// if $particles > -1, you've gotten a value for it.
			// that means that the next line will be the
			// ozone reading, if you haven't already gotten
			// a reading for ozone (i.e. if $ozone == -1):
			if (($particles > -1) && ($ozone == -1)) {
				$readOzone = 1;
			}
		}
     }  
    // close the file at the URL, you're done: 
    fclose($filePath);
?>