I want to call the php function by html button or javascript code. for example if I click a button, a php function should display or do some function. I know ajax is the only way to do this, but I could not understand the ajax code for simply call the function, so please anyone give a simple example ajax code to control the php function by html button. and please do not give any code with jquery or any other library, because I not yet learn any libraries for php or javascript.