Files with specific extensions are not getting attached - php

Question

I'm creating a form where I've a place for attaching files. But, files with specific extensions like .xls, .sql etc., are not getting attached. But, other files like .docx, .pdf etc., are getting attached. This is how I tried:
function file_upload($control_id, $target_directory) {
if(isset_file($control_id)) {
if(file_exists($target_directory) == false) {
mkdir($target_directory, 0777, true); //to be create the directory recursively
}
$file_name = basename($_FILES[$control_id]["name"]); //to be get file name
write_log($file_name);
$file_extension = pathinfo($file_name, PATHINFO_EXTENSION); //to be get file extension
write_log($file_extension);
$file_size = $_FILES[$control_id]["size"]; //to be get file size in bytes
write_log($file_size);
$target_file_name = round(microtime(true) * 1000).".".$file_extension; //to be get target file name
$target_file_path = $target_directory.$target_file_name; //to be get target file
if(file_exists($target_file_path) == true) {
chmod($target_file_path, 0755); //Change the file permissions if allowed
unlink($target_file_path); //remove the file
}
if (move_uploaded_file($_FILES[$control_id]["tmp_name"], $target_file_path) == true) {
$arr = array(
"status" => true,
"message" => "The file ".$file_name." has been uploaded.",
"file_name" => $file_name,
"file_extension" => $file_extension,
"file_size" => $file_size,
"uploaded_file_name" => $target_file_name,
"uploaded_file_path" => $target_file_path
);
} else {
$arr = array(
"status" => false,
"message" => "Sorry, there was an error uploading your file."
);
}
} else {
$arr = array(
"status" => false,
"message" => "Please select file"
);
}
//echo json_encode($arr);
return $arr;
}
$id = intval(mysqli_real_escape_string($mysqli, $_REQUEST["id"]));
$upload_directory = "uploads/attachments/";
$result = file_upload("contract_attachment", "../".$upload_directory);
if($result[status] == true) {
$query = "insert into `attachments`
(
`id`,
`file_name`,
`file_extension`,
`file_size`,
`uploaded_file_name`,
`uploaded_file_path`
)
values
(
'id',
'".addslashes($result['file_name'])."',
'".$result[file_extension]."',
'".$result[file_size]."',
'".$result[uploaded_file_name]."',
'".$upload_directory.$result[uploaded_file_name]."'
)";
mysqli_query($mysqli, $query) or throwexception(mysqli_error($mysqli));
}
echo json_encode(array("message" => "Record submitted successfully"));
exit;
The problem is, when ever I try to attach a file with extension .xls or .sql, the $file_name, $file_extension, $file_size will get a value. For example, if the file I'm attaching is format.xls, it showed $file_name = format, $file_extension = .xls and $file_size = 0. Since the file size it's taking is zero, the condition "$result[status]" fails. So, the file is not getting attached.
If I attach files like .pdf or .docx I get the correct values. For example, if I attach file like format.pdf, it showed $file_name = format, $file_extension = .pdf, $file_size = 9824. And the file is also getting attached.
But, I don't know what's wrong with this code, since files with extensions .xls and .sql are not getting attached. Can someone correct this and tell whats wrong with this?