PHP - Review My Freelance(?) Site

Dear Friends.

Just now I tried to create PHP to make Rest API for my mobile application and I would like to know that it's good coding and need any improve? it is my first time for Rest API. normally I just connect to PHP file directly

on .htaccess

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([0-9A-Za-z_]+)$ function.php?func=$1 [L,QSA]
RewriteRule ^([0-9A-Za-z_]+)/$ function.php?func=$1 [L,QSA]

on function.php

$func = $_GET['func'];
switch( $func) 
{
	case 'lab_info':		//ໜ້າຫຼັກ
		define( '_FUNC', 'lab_info.php');
		break;

	case 'customer_info':		//ຂໍ້ມູນຜູ້ໃຊ້
		define( '_FUNC', 'customer_info.php');
		break;
	default:			// No function
		define( '_FUNC', 'functionnotfound.php');
		break;
}

if( defined( '_FUNC') && constant( '_FUNC') !='')
	require( "func/" . _FUNC);

on customer_info.php

$error = array();
if(isset($_POST['user']) != 'lung'){
    $error['status'] = "422";
    $error['title'] = "Authentication Fail";
    $error['detail'] = "Invalid user authentication";

    echo json_encode($error);die();
}
if(!isset($_POST['user'])){
    $error['status'] = "401";
    $error['title'] = "Invalid Attribute";
    $error['detail'] = "Invalid Attribute For Information";

    echo json_encode($error);die();

}

$result = $conn->query("select Lab_Name,Lab_Username,Lab_Password from tb_labmanagers");
$customer = array();
while($row =mysqli_fetch_assoc($result))
{
    $customer[] = $row;
}

echo json_encode($customer);

this image attached file is result from postman, client need to send user = 'lung' to get information

<?php

$cfg['routes'] = [
    'cars/(:any)/(:any)/(:num).php' => 'cars/$3/$1/$2',
    'default_route'                 => 'cars/index',
    'trucks/parts?year=(:num)'      => 'parts/trucks/$1',
    'vans/articles(:any)'           => 'articles$1' 
];

$uris = [
    'cars/toyota/tercel/2014.php', # /cars/2014/toyota/tercel
    'default_route',               # /cars/index
    'trucks/parts?year=2014',      # /parts/trucks/2014
    'vans/articles?p=42342'        # /articles?p=42342
];

$i = 0;
foreach( $cfg['routes'] as $k => $v )
{
    $k = '|^' . preg_quote( $k ) . '$|uiD';

    $k = str_replace(
        [
            '\(\:any\)',
            '\(\:alnum\)',
            '\(\:num\)',
            '\(\:alpha\)',
            '\(\:segment\)'
        ], [
            '(.+)',
            '([[:alnum:]]+)',
            '([[:digit:]]+)',
            '([[:alpha:]]+)',
            '([^/]*)'
        ], 
        $k
    );

    echo '<br />' . $uris[$i] . '<br />' . $k . '<br />';
    
    if( @preg_match( $k, $uris[$i] ) )
    {
        echo preg_replace( $k, $v, $uris[$i] ) . '<br /><br />';
    }

    $i++;
}

	if(get_images_for_delete($username, $newid, $mysqli) !== FALSE){
	// WE are dealing with images
	$images = get_images_for_delete($username, $newid, $mysqli);
	$sourceBucket = "***********";
	$targetBucket = "***********";
	foreach($images as $image){
	// copy our object
	$aws = new s3;
	$aws = $aws->copyObject($targetBucket, $image, $sourceBucket, $image);
	// delete our object
	$aws_delete = new s3;
	$aws_delete = $aws_delete->deleteObject($image);
	// copy our (thumbnail) object
	$aws2 = new s3;
	$aws2 = $aws2->copyObject($targetBucket, "thumb_".$image, $sourceBucket, "thumb_".$image);
	// delete our (thumbnail) object
	$aws_delete2 = new s3;
	$aws_delete2 = $aws_delete2->deleteObject("thumb_".$image);
	}

/var/www/html/site1/index.php
/var/www/html/site1/administrator/index.php
/var/www/html/site2/index.php
/var/www/html/site2/administrator/index.php
/var/www/html/site3/index.php
/var/www/html/site3/administrator/index.php