Uncaught TypeError: $ is not a function

<?php require_once(dirname(__FILE__).'/../config.php'); ?>
<?php header("Content-type: text/javascript"); ?>
 
(function(){
if(!window.alreadyIncluded) {/** Check if file is already loaded **/
var t = 0;
/******** Main Function That Will Generate All Ads *********/
function main() {
var g = $(".<?php echo ADS_CLASS_NAME;?>").map(function () {
 
t++;
    /*** GET TAGS ***/
if ( $(document).find("title").text() ) {
    var title = $(document).find("title").text().replace(/ /g, ',');
} else {
    var title = "";
}
 
if ( $(document).find('meta[name=description]').attr("content") ) {
    var description = $(document).find('meta[name=description]').attr("content").replace(/ /g, ',');
} else {
    var description = "";
}
 
if ( $(document).find('meta[name=keywords]').attr("content") ) {
    var keywords = $(document).find('meta[name=keywords]').attr("content").replace(/ /g, ',');
} else {
    var keywords = "";
}
    var rf      =   document.referrer;
    var lh      =   window.location.host;
    var st      =   title + "," + description + "," + keywords;
    var st      =   st.replace("(", "").replace(")", "");
    var slot    =   $( this ).data("ad-slot");
    var client  =   $( this ).data("ad-client");
    var width   =   $( this ).width();
    var height  =   $( this ).height();
 
    $( this ).html( '<iframe id="ad_iframe_' + t + '" name="ad_iframe_' + t + '" width="'+ width +'" height="'+ height +'" frameborder="0" marginwidth="0" marginheight="0" vspace="0" hspace="0" allowtransparency="true" scrolling="no" src="<?php echo HTTP_SERVER_WEBSITE ?>pagead/generate?s=' + slot + '&c=' + client + '&st=' + st + '&rf=' + rf + '&lh=' + lh + '&ct=' + t + '"></iframe>' );
 
}).get();
}
/******** End Main Function That Will Generate All Ads *********/
 
/******** Load jQuery if not present *********/
if ( typeof jQuery === "undefined" ) {
    var script_tag = document.createElement('script');
    script_tag.setAttribute("type","text/javascript");
    script_tag.setAttribute("src", "//ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js")
    script_tag.onload = main; //Run main() once jQuery has loaded
    script_tag.onreadystatechange = function () { //Same thing but for IE
        if (this.readyState == 'complete' || this.readyState == 'loaded') main();
    } //onreadystatechange.function
    document.getElementsByTagName("head")[0].appendChild(script_tag);
    } else {
        main();
} //if.jQuery
/******** END Load jQuery if not present *********/
 
window.alreadyIncluded = true;
} /*** End check if file is already loaded ***/
})()