function substr (str, start, len) {
    // Returns part of a string  
    // 
    // version: 909.322
    // discuss at: http://phpjs.org/functions/substr
    // +     original by: Martijn Wieringa
    // +     bugfixed by: T.Wild
    // +      tweaked by: Onno Marsman
    // +      revised by: Theriault
    // *       example 1: substr('abcdef', 0, -1);
    // *       returns 1: 'abcde'
    // *       example 2: substr(2, 0, -6);
    // *       returns 2: false

// Add: (?) Use unicode.semantics and/or unicode.runtime_encoding (e.g., with string wrapped in "binary" or "Binary" class) to
// allow access of binary (see file_get_contents()) by: charCodeAt(x) & 0xFF (see https://developer.mozilla.org/En/Using_XMLHttpRequest )
// Fix: Handle 4-byte characters

    str += '';
    var end = str.length;
    if (start < 0) {
        start += end;
    }
    end = typeof len === 'undefined' ? end : (len < 0 ? len + end : len + start);
    // PHP returns false if start does not fall within the string.
    // PHP returns false if the calculated end comes before the calculated start.
    // PHP returns an empty string if start and end are the same.
    // Otherwise, PHP returns the portion of the string from start to end.
    return start >= str.length || start < 0 || start > end ? !1 : str.slice(start, end);
}

function strlen (string) {
    // http://kevin.vanzonneveld.net
    // +   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;
}

function addslashes (str) {
    // http://kevin.vanzonneveld.net
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: Ates Goral (http://magnetiq.com)
    // +   improved by: marrtins
    // +   improved by: Nate
    // +   improved by: Onno Marsman
    // +   input by: Denny Wardhana
    // +   improved by: Brett Zamir (http://brett-zamir.me)
    // *     example 1: addslashes("kevin's birthday");
    // *     returns 1: 'kevin\'s birthday'
 
    return (str+'').replace(/([\\"'])/g, "\\$1").replace(/\u0000/g, "\\0");
}

function trim (str, charlist) {
    // http://kevin.vanzonneveld.net
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: mdsjack (http://www.mdsjack.bo.it)
    // +   improved by: Alexander Ermolaev (http://snippets.dzone.com/user/AlexanderErmolaev)
    // +      input by: Erkekjetter
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +      input by: DxGx
    // +   improved by: Steven Levithan (http://blog.stevenlevithan.com)
    // +    tweaked by: Jack
    // +   bugfixed by: Onno Marsman
    // *     example 1: trim('    Kevin van Zonneveld    ');
    // *     returns 1: 'Kevin van Zonneveld'
    // *     example 2: trim('Hello World', 'Hdle');
    // *     returns 2: 'o Wor'
    // *     example 3: trim(16, 1);
    // *     returns 3: 6

    var whitespace, l = 0, i = 0;
    str += '';
    
    if (!charlist) {
        // default list
        whitespace = " \n\r\t\f\x0b\xa0\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u200b\u2028\u2029\u3000";
    } else {
        // preg_quote custom list
        charlist += '';
        whitespace = charlist.replace(/([\[\]\(\)\.\?\/\*\{\}\+\$\^\:])/g, '$1');
    }
    
    l = str.length;
    for (i = 0; i < l; i++) {
        if (whitespace.indexOf(str.charAt(i)) === -1) {
            str = str.substring(i);
            break;
        }
    }
    
    l = str.length;
    for (i = l - 1; i >= 0; i--) {
        if (whitespace.indexOf(str.charAt(i)) === -1) {
            str = str.substring(0, i + 1);
            break;
        }
    }
    
    return whitespace.indexOf(str.charAt(0)) === -1 ? str : '';
}