Why won't custom WordPress page load get_posts array data? - custom-wordpress-pages

Question

I've got 3 separate files.
Forms (a basic wordpress page built within Wordpress). The data here shows up fine and works as expected.
<div class="select-wrapper">
<select class="paybill" name="provider-name" id="provider-name" onchange="formFilter(this.value)">
<option value="" disabled selected hidden>- Choose a Provider -</option>
<?php foreach( $providerslist as $providerlist ) {
$theprovidernname = get_the_title($providerlist);
$providerlocations = get_field('provider_locations', $providerlist);
$pcount = count($providerlocations);
for($i = 0; $i < $pcount; $i++){
$location_name = get_field_object('location_name', $providerlocations[$i]);
if(!empty($location_name)){
break;
}
}
if(empty($location_name)){
$location_name = array(value=>"TEXT");
}?>
<option value="<?php echo $location_name['value']?>"><?php echo $theprovidernname; ?></option>
<?php } ?>
</select>
</div>
A filtering Javascript file. The purpose of this file is to get the data from the select field and pass it using AJAX to the 3rd PHP file.
function formFilter(str){
//clears previous results
document.getElementById("form-results").innerHTML = "";
var value = str.value;
console.log(value);
if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
var xmlhttp = new XMLHttpRequest();
} else {// code for IE6, IE5
var xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200){
document.getElementById("form-results").innerHTML = xmlhttp.responseText;
}
}
xmlhttp.open("GET",".../framework-forms-results.php?location="+value,true);
xmlhttp.send();
}
A custom PHP file living in the Child Theme folder of the site. What I'm trying to do is call a custom post type called 'location' and then work through the data. On other pages I'm able to get this exact code to work just fine but here it will not work at all. This is the entirety of this Page at the moment. If I remove the get_posts code and just echo some text, it will return the text so I know the issue is with the get_posts call. I just can't figure out why. If I try to load this page alone without going through the select options, it still returns a 500 error.
//Create Array of All Locations
$locations = get_posts(array(
'posts_per_page' => -1,
'post_type' => 'location',
));
print "<pre>";
print_r($locations);
print "</pre>";
Any thoughts as to why the get_posts call won't work on this custom page but will work if it's used via shortcodes on pages built within wordpress?
I've tried debugging, logging errors and reviewing the logs. I've tried to require the blog header to bring in other necessary files but nothing.

Answer 1

If you are calling this URL directly, which is not how WordPress ajax is intended to work, you can still get this code to run by adding this PHP code:
$parse_uri = explode( 'wp-content', $_SERVER['SCRIPT_FILENAME'] );
require_once( $parse_uri[0] . 'wp-load.php' ); to the top of the file.
Link: https://codex.wordpress.org/AJAX_in_Plugins (I know this says Ajax in plugins but this is also what you would do if developing a custom theme to keep your code WordPress-y).