function strip_tags(str, allowed_tags) {
    // http://kevin.vanzonneveld.net
    // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   improved by: Luke Godfrey
    // +      input by: Pul
    // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   bugfixed by: Onno Marsman
    // +      input by: Alex
    // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +      input by: Marc Palau
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // *     example 1: strip_tags('<p>Kevin</p> <br /><b>van</b> <i>Zonneveld</i>', '<i><b>');
    // *     returns 1: 'Kevin <b>van</b> <i>Zonneveld</i>'
    // *     example 2: strip_tags('<p>Kevin <img src="someimage.png" onmouseover="someFunction()">van <i>Zonneveld</i></p>', '<p>');
    // *     returns 2: '<p>Kevin van Zonneveld</p>'
    // *     example 3: strip_tags("<a href='http://kevin.vanzonneveld.net'>Kevin van Zonneveld</a>", "<a>");
    // *     returns 3: '<a href='http://kevin.vanzonneveld.net'>Kevin van Zonneveld</a>'
 
    var key = '', tag = '', allowed = false;
    var matches = allowed_array = [];
 
    var replacer = function(search, replace, str) {
        return str.split(search).join(replace);
    };
 
    // Build allowes tags associative array
    if (allowed_tags) {
        allowed_array = allowed_tags.match(/([a-zA-Z]+)/gi);
    }
  
    str += '';
 
    // Match tags
    matches = str.match(/(<\/?[^>]+>)/gi);
 
    // Go through all HTML tags
    for (key in matches) {
        if (isNaN(key)) {
            // IE7 Hack
            continue;
        }
 
        // Save HTML tag
        html = matches[key].toString();
 
        // Is tag not in allowed list? Remove from str!
        allowed = false;
 
        // Go through all allowed tags
        for (k in allowed_array) {
            // Init
            allowed_tag = allowed_array[k];
            i = -1;
 
            if (i != 0) { i = html.toLowerCase().indexOf('<'+allowed_tag+'>');}
            if (i != 0) { i = html.toLowerCase().indexOf('<'+allowed_tag+' ');}
            if (i != 0) { i = html.toLowerCase().indexOf('</'+allowed_tag)   ;}
 
            // Determine
            if (i == 0) {
                allowed = true;
                break;
            }
        }
 
        if (!allowed) {
            str = replacer(html, "", str); // Custom replace. No regexing
        }
    }
 
    return str;
}


function str_ireplace( search, replace, subject ) {
    // http://kevin.vanzonneveld.net
    // +   original by: Martijn Wieringa
    // +      input by: penutbutterjelly
    // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +    tweaked by: Jack
    // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
    // +   bugfixed by: Onno Marsman
    // *     example 1: str_ireplace('l', 'l', 'HeLLo');
    // *     returns 1: 'Hello'
 
    var i, k = '';
    var searchl = 0;
 
    search += '';
    searchl = search.length;
    if (!(replace instanceof Array)) {
        replace = new Array(replace);
        if (search instanceof Array) {
            // If search is an array and replace is a string,
            // then this replacement string is used for every value of search
            while (searchl > replace.length) {
                replace[replace.length] = replace[0];
            }
        }
    }
 
    if (!(search instanceof Array)) {
        search = new Array(search);
    }
    while (search.length>replace.length) {
        // If replace has fewer values than search,
        // then an empty string is used for the rest of replacement values
        replace[replace.length] = '';
    }
 
    if (subject instanceof Array) {
        // If subject is an array, then the search and replace is performed
        // with every entry of subject , and the return value is an array as well.
        for (k in subject) {
            subject[k] = str_ireplace(search, replace, subject[k]);
        }
        return subject;
    }
 
    searchl = search.length;
    for (i = 0; i < searchl; i++) {
        reg = new RegExp(search[i], 'gi');
        subject = subject.replace(reg, replace[i]);
    }
 
    return subject;
}