index.php

<?php
// PHP REST API FILE UPLOAD
// source: https://www.onlyxcodes.com/2021/03/php-rest-api-file-upload.html

header("Content-Type: application/json");
header("Access-Control-Allow-Origin: *");
header("Access-Control-Allow-Methods: POST");
header("Access-Control-Allow-Headers: Access-Control-Allow-Headers, Content-Type, Access-Control-Allow-Methods, Authorization");

$data = json_decode(file_get_contents("php://input"), true); // collect input parameters and convert into readable format
	
$fileName  =  $_FILES['file']['name'];
$tempPath  =  $_FILES['file']['tmp_name'];
$fileSize  =  $_FILES['file']['size'];

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
 	$errorMSG = json_encode(array("message" => "Method not found", "status" => false));
	http_response_code(404);
	echo $errorMSG;
} else {
    if (empty($fileName)) {
    	$errorMSG = json_encode(array("message" => "Please select file", "status" => false));
    	http_response_code(400);
    	echo $errorMSG;
    } else {
        $timestamp = new DateTime();
        $newFileName = $timestamp->getTimestamp();
        $fileName = str_replace(' ', '-', $fileName);
        $fileName = "{$newFileName}-{$fileName}";
    
    	$upload_path = 'files/'; // set upload folder path 
    	
    	$fileExt = strtolower(pathinfo($fileName, PATHINFO_EXTENSION)); // get file extension
    		
    	// invalid file extensions
    	$valid_extensions = array('php', 'sql'); 
    					
    	// do not allow invalid file formats
    	if (in_array($fileExt, $valid_extensions)) {
    		$errorMSG = json_encode(array("message" => "Forbidden file type: {$fileExt}", "status" => false));	
    		http_response_code(400);
    		echo $errorMSG;
    	} else {
    		// check file size '2MB', default max limit is 2MB, if you want increase, configure php server
    		if ($fileSize < 2000000 && $fileSize > 0){
    			move_uploaded_file($tempPath, $upload_path . $fileName); // move file from system temporary path to our upload folder path 
    		} else {		
    			$errorMSG = json_encode(array("message" => "Sorry, your file is too large, please upload 2 MB size", "status" => false));
				http_response_code(400);
    			echo $errorMSG;
    		}
    	}
    }
    
    // if no error caused, continue
    if (!isset($errorMSG)) {
    	echo json_encode(array("message" => "File uploaded successfully", "status" => true, "name" => "{$upload_path}{$fileName}", "url" => "https://your-site.com/{$upload_path}{$fileName}"));	
    }
}

?>