JS Antivirus

<?php

// Get file list
$filelist = "all_js_files_list.txt";
//$filelist = "test_js_files.txt";
$log_file = "js_antivirus.log";

$fp = fopen($filelist, "r");
$fp_log = fopen($log_file, "a");
if( $fp )
{
    fwrite($fp_log, "\n\n=========================\n");
    fwrite($fp_log, "Start JS antivirus clean\n");
    fwrite($fp_log, date("Y-m-d H:i:s")."\n");
    fwrite($fp_log, "=========================\n");

    while( ($filename = fgets($fp)) !== false )
    {
        $filename = trim($filename);
        if( file_exists($filename) )
        {
            // Run antivirus
            $content = file_get_contents($filename);
            $res = virus_clear($content);
            if( $res )
            {
                file_put_contents($filename, $content);
                echo "$filename - OK\n";
                fwrite($fp_log, "$filename - OK\n");
            }
            else
            {
                echo "$filename - not found\n";
                fwrite($fp_log, "$filename - not found\n");
            }
        }
        else
        {
            echo "File not exists: $filename\n";
            fwrite($fp_log, "File not exists: $filename\n");
        }
    }

    if (!feof($fp))
    {
        echo "Error: unexpected fgets() fail\n";
        fwrite($fp_log, "Error: unexpected fgets() fail\n");
    }
    fclose($fp_log);
    fclose($fp);
}




function virus_clear(&$js)
{
    $js_lenght = strlen($js);
    $max_length = min($js_lenght, 2000);

    $js_slice = substr($js, 0-$max_length);

    $keys = array();
    $found = false;
    if( preg_match_all("#([\d\w]+)\(([\d\w]+)\(([\d\w]+)\[\d+\]\)\);#is", $js_slice, $match) && isset($match[3][0]) )
    {
        foreach( $match[0] as $m_i=>$fns_full )
        {
            $fns1 = $match[1][$m_i];
            $fns2 = $match[2][$m_i];
            $var = $match[3][$m_i];

            if( preg_match("#var\s$var=\[[\"'\d,]{100,}\];#is", $js_slice, $match2) && isset($match2) )
            {
                if( preg_match("#function\s$fns2\([\d\w]+\){return\s([\d\w]+)\(([\d\w]+)#is", $js_slice, $match3) && isset($match3) )
                {
                    $keys = array(
                        $fns_full,
                        'function '.$fns1,
                        'function '.$fns2,
                        $match2[0],
                        $match3[0],
                        'function '.$match3[1],
                        'function '.$match3[2]
                    );
                }
            }

            if( $keys )
            {
                $pos = array();
                foreach( $keys as $key ) $pos[] = strpos($js_slice, $key);
                $pos = min($pos);
                //$lenght = strlen($js_slice)-$pos;

                // Caught!
                //if( $pos && $lenght <= $max_length )
                //{
                    $js_slice = substr($js_slice, 0, $pos);
                    $found = true;
                //}
            }
        }
    }

    if( $found )
    {
        $js = substr($js, 0, 0-$max_length) . $js_slice;
    }

    return $found;
}