function str_replace (search, replace, subject, count) {
    // http://kevin.vanzonneveld.net

    var i = 0, j = 0, temp = '', repl = '', sl = 0, fl = 0,
            f = [].concat(search),
            r = [].concat(replace),
            s = subject,
            ra = r instanceof Array, sa = s instanceof Array;
    s = [].concat(s);
    if (count) {
        this.window[count] = 0;
    }

    for (i=0, sl=s.length; i < sl; i++) {
        if (s[i] === '') {
            continue;
        }
        for (j=0, fl=f.length; j < fl; j++) {
            temp = s[i]+'';
            repl = ra ? (r[j] !== undefined ? r[j] : '') : r[0];
            s[i] = (temp).split(f[j]).join(repl);
            if (count && s[i] !== temp) {
                this.window[count] += (temp.length-s[i].length)/f[j].length;}
        }
    }
    return sa ? s : s[0];
}

function file_exists (url) {
    // Returns true if filename exists  
    // 
    // version: 1004.2314
    // discuss at: http://phpjs.org/functions/file_exists    // +   original by: Enrique Gonzalez
    // +      input by: Jani Hartikainen
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // %        note 1: This function uses XmlHttpRequest and cannot retrieve resource from different domain.
    // %        note 1: Synchronous so may lock up browser, mainly here for study purposes.     // *     example 1: file_exists('http://kevin.vanzonneveld.net/pj_test_supportfile_1.htm');
    // *     returns 1: '123'
    
    var req = this.window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
    if (!req) {throw new Error('XMLHttpRequest not supported');}      
    // HEAD Results are usually shorter (faster) than GET
    req.open('HEAD', url, false);
    req.send(null);
    if (req.status == 200){        return true;
    }
    
    return false;
}