Why is my function returning NULL?
<pre><code>function csv_data_to_zip_array($csv)
{
    $f = fopen($csv, "r");
    $i= 0;
    while($line= fgets($f)){
        $line = preg_replace("/[^0-9]/", "", $line);
        if(is_numeric($line)&amp;&amp;strlen($line)==5){ // it is a zip code
            $array[] = $line;
        }
        $i++;
    }
    fclose($f);
    return $array;
}
</code></pre>

<p>That is my function, it's reading a large csv with a bunch of zip codes into an array.</p>
