Craigslist Monitor and Text Alert System

<?php
require_once 'phpdom.php';

function remove_non_numeric($string) {
    return preg_replace('/\D/', '', $string);
}

function sendAlert($body){
    $header = array();
    $headers[] = 'Content-Transfer-Encoding: 7bit';
    $headers[] = 'From: ';
    mail('', 'Craigslist', $body, implode("\r\n", $headers));
}

function crawl(){
    $ret = array();
    $save = array();
    $cities = array(
        'hickory',
        'charlotte'
    );
    $keywords = array(
        'washer'=>250,
        'dryer'=>250,
        'stove'=>150,
        'range'=>150,
        'oven'=>150,
        'refrigerator'=>250,
        'refridgerator'=>250,
        'fridge'=>250
    );
    $blacklist = array(
        'gas',
        'dishwasher',
        'microwave',
        'toaster'
    );
    $f='save.json';
    $oldsavedata = file_get_contents($f);
    if ($oldsavedata === false) echo "Cannot open file ($f)<br/><br/>";
    $oldsave = json_decode($oldsavedata,true);
    foreach ($cities as $city) {
        $html = file_get_html('http://'.$city.'.craigslist.org/ppa/');
        $ret[$city] = array();
        foreach ($html->find('p.row') as $index=>$row) {
            $valid = true;
            $item = $row->innertext;
            $link = $row->find('a', 0);
            $linktext = $link->plaintext;
            $smalltext = strtolower($linktext);
            $href = $link->href;
            $type = $row->find('a', 1)->plaintext;
            $price = remove_non_numeric($row->find('span.itempp', 0)->plaintext);
            if (0 === $index) $save[$city] = $href;
            if ($href == $oldsave[$city]) break;
            if ($type === 'appliances - by dealer') continue;
            foreach ($blacklist as $black) {
                if (-1 < strpos($smalltext, $black)) {
                    $valid = false;
                    break;
                }
            }
            if ($valid !== true) continue;
            foreach ($keywords as $keyword=>$value) {
                if (-1 < strpos($smalltext, $keyword) && (int)$price < $value) {
                    array_push($ret[$city], '$'.$price.' - '.$linktext);
                    break;
                }
            }
        }
    }
    $save = json_encode($save);
    if ($oldsavedata == $save) die('No new postings.');
    if (is_writable($f)) {
        if (!$handle = fopen($f, 'w')) {
             echo "Cannot open file ($f)";
             exit;
        }
        if (fwrite($handle, $save) === false) {
            echo "Cannot write to file ($f)";
            exit;
        }
        echo "Success, wrote data to file ($f)";
        fclose($handle);
    } else echo "The file $f is not writable";
    return $ret;
}

$current_time = date('G');
if ($current_time >= 7 && $current_time <= 24) {
    $data = crawl();
    $body = '';
    $citycount = 1;
    foreach ($data as $city=>$items) {
        if (1 > count($items)) continue;
        if ($citycount > 1) $body .= "\r\n\r\n".strtoupper($city)."\r\n\r\n";
        else $body .= strtoupper($city)."\r\n\r\n";
        foreach ($items as $item) {
            $body .= ucwords(strtolower(htmlspecialchars_decode($item)))."\r\n";
        }
        $citycount++;
    }
    if (0 < strlen($body)) {
        sendAlert($body);
        print_r($data);
    }
}
?>