Execute a PHP function in a file of functions from a JavaScript function -

i want call php function javascript function.

"why?" might ask?

i have series of php functions organized in separate file custom_functions.php

i learning how build javascript , jquery how bridging gap. more familiar php, finding way through window.

i have list of elements constructed in index.php. list of items constructed on fly database , id attribute created based on id of record:

echo "<span id="content_" . $row{'unique_id'} . "\" onclick=\"displaydetails(" . $row{'unique_id'} . ")\">"; 

displaydetails(record_no) javascript function in external javascript file.

for tried this:

function displaydetails(record){     data = {};     //data = <?php retrievecontent(content_id); ?>     $('.output').html("testing function - section " + section_number); } 

but of course not work because php server side action , javascript client-side action.

my particular problem enough different this one leave me stumped.

i have php file , within want ajax call specific function range of functions in file.

what's not clear how call function in file ajax. pass in url this: "custom_functions.php?functionname=displaydetails&record=<some number>" ?

for now, not want use jquery ajax, i'd understand fundamentals of xmlhttprequest purely pure javascript/dom perspective.

yes, have call php file mentioned.

when calling php script ajax, return data json formation. echo in php become ajax result.

and javascript job creating elements show , inject data.

however, can inject result html of php script directly dom.

example1: injecting ajax response data directly dom

javascript

axios.get('/example_api.php').then(resp => {     // in case, gonna put response data innerhtml wanna show.     somedomeelement.innerhtml = resp.data; }); 

php (example_api.php)

echo "<p>hello world</p>"; 

https://developer.mozilla.org/en-us/docs/web/api/xmlhttprequest

example2: when ajax response data json

javascript

axios.get('/example_api.php').then(resp => {     resp.data.foreach(function(item) {        // in case, have create dom elements show data         createelement(item);      }); }); 

php(example_api.php)

echo json_encode(array('data1', 'data2')); 

update

i update answer here if comment more questions.