PHP service call using JavaScript

jQuery.ajax({
type: "POST",
url: 'http://localhost/SampleService/MyService.php',
dataType: 'json',
data: {functionname: 'Function_A',Parameter_A: "value A",Parameter_B: "value B"},
beforeSend: function (jqXHR, Settings) {
jqXHR.url = Settings.url;
$("#ShowPreLoader").show();
},
success: function (obj, textstatus) {

});
},
complete: function () {
$("#ShowPreLoader").hide();

}
});

In your PHP MyService.php

switch($_POST['functionname']) {
case 'Function_A':Function_A($_POST['Parameter_A'],$_POST['Parameter_B']);
break;
case 'Function_B':Function_B($_POST['Parameter_C']);
break;
case 'Function_C':Function_C();
break;
}

function Function_A($Parameter_A,$Parameter_B)
{
print_r(json_encode($ResultArray));
}