PHP doesn't send the reposnse - php

Question

I have a very weird problem with php and I can't find any explanation for it.
I want to add this line of code to grab extension from the sent file:
$extension = array_pop( explode( "." , $_FILES["myFiles"]["name"][$key]);
but if i do so php doens't send a respond although the file is saved successfully. If I simply delete this line and hardcode ".jpg" instead $extension it sends the response as expected.
<?php
$response = array();
if (isset($_FILES)) {
foreach ($_FILES["myFiles"]["tmp_name"] as $key => $value) {
$user = $_POST["user"];
// when i add the line below it deosn't send the response!
$extension = array_pop( explode( "." , $_FILES["myFiles"]["name"][$key]) );
move_uploaded_file($value, "uploads/$user.$extension");
};
$response["msg"] = "image has been uploaded";
} else {
$response["msg"] = "selcect an image";
}
echo json_encode($response);

Answer 1

array_pop takes argument by reference. You can't provide argument directly from another function to array_pop.
Instead in your case you should do this:
$parts = explode("." , $_FILES["myFiles"]["name"][$key]);
$extension = array_pop($parts);
But! You should NEVER trust client's data, even if it's just a file extension. It is better to check extension itself (is it jpg, png, svg, gif), also check if the file is really an image, check size of that image, etc...