u can use ajax. u must create a function in your javascript code that send ajax request to your php file and get response from that.

function getXMLHttpRequest()
{
if (window.XMLHttpRequest) {
return new window.XMLHttpRequest;
}
else {
try {
return new ActiveXObject("MSXML2.XMLHTTP.3.0");
}
catch(ex) {
return null;
}
}
}

function do_somting(){
xhr= getXMLHttpRequest();
xhr.onreadystatechange=function()
{

        if(xhr.readyState==4 && xhr.status==200)
        {
            //get response here from php file with xhr.responseText;
            
        }
    }
    xhr.open("GET","file.php",true);
    xhr.send(null); 

}

and in php file that contains php functions.