function str_replace (search, replace, subject, count) {
    // Replaces all occurrences of search in haystack with replace  
    // 
    // version: 909.322
    // discuss at: http://phpjs.org/functions/str_replace
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: Gabriel Paderni
    // +   improved by: Philip Peterson
    // +   improved by: Simon Willison (http://simonwillison.net)
    // +    revised by: Jonas Raoni Soares Silva (http://www.jsfromhell.com)
    // +   bugfixed by: Anton Ongson
    // +      input by: Onno Marsman
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +    tweaked by: Onno Marsman
    // +      input by: Brett Zamir (http://brett-zamir.me)
    // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   input by: Oleg Eremeev
    // +   improved by: Brett Zamir (http://brett-zamir.me)
    // +   bugfixed by: Oleg Eremeev
    // %          note 1: The count parameter must be passed as a string in order
    // %          note 1:  to find a global variable in which the result will be given
    // *     example 1: str_replace(' ', '.', 'Kevin van Zonneveld');
    // *     returns 1: 'Kevin.van.Zonneveld'
    // *     example 2: str_replace(['{name}', 'l'], ['hello', 'm'], '{name}, lars');
    // *     returns 2: 'hemmo, mars'
    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 strlen (string) {
    // Get string length  
    // 
    // version: 909.322
    // discuss at: http://phpjs.org/functions/strlen
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: Sakimori
    // +      input by: Kirk Strobeck
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   bugfixed by: Onno Marsman
    // +    revised by: Brett Zamir (http://brett-zamir.me)
    // %        note 1: May look like overkill, but in order to be truly faithful to handling all Unicode
    // %        note 1: characters and to this function in PHP which does not count the number of bytes
    // %        note 1: but counts the number of characters, something like this is really necessary.
    // *     example 1: strlen('Kevin van Zonneveld');
    // *     returns 1: 19
    // *     example 2: strlen('A\ud87e\udc04Z');
    // *     returns 2: 3
    var str = string+'';
    var i = 0, chr = '', lgth = 0;

    var getWholeChar = function (str, i) {
        var code = str.charCodeAt(i);
        var next = '', prev = '';
        if (0xD800 <= code && code <= 0xDBFF) { // High surrogate (could change last hex to 0xDB7F to treat high private surrogates as single characters)
            if (str.length <= (i+1))  {
                throw 'High surrogate without following low surrogate';
            }
            next = str.charCodeAt(i+1);
            if (0xDC00 > next || next > 0xDFFF) {
                throw 'High surrogate without following low surrogate';
            }
            return str.charAt(i)+str.charAt(i+1);
        } else if (0xDC00 <= code && code <= 0xDFFF) { // Low surrogate
            if (i === 0) {
                throw 'Low surrogate without preceding high surrogate';
            }
            prev = str.charCodeAt(i-1);
            if (0xD800 > prev || prev > 0xDBFF) { //(could change last hex to 0xDB7F to treat high private surrogates as single characters)
                throw 'Low surrogate without preceding high surrogate';
            }
            return false; // We can pass over low surrogates now as the second component in a pair which we have already processed
        }
        return str.charAt(i);
    };

    for (i=0, lgth=0; i < str.length; i++) {
        if ((chr = getWholeChar(str, i)) === false) {
            continue;
        } // Adapt this line at the top of any loop, passing in the whole string and the current iteration and returning a variable to represent the individual character; purpose is to treat the first part of a surrogate pair as the whole character and then ignore the second part
        lgth++;
    }
    return lgth;
}