Error uploading a file in PHP

I'm trying to upload a file to an Aruba VPS with CentOS using php.

The php code is as follows:

<?php
    session_start();
    require 'conexion.php';
    use baseDeDatos\conexion as conexion;

    $target_file = "pdf/englishtest"."_".date("F")."_".rand(0,1000).substr(basename($_FILES["fileToUpload"]["name"]),-4);
    $uploadOk = 1;
    $imageFileType = strtolower(pathinfo($target_file,PATHINFO_EXTENSION));
    // Check if image file is a actual image or fake image
    if(isset($_POST["submit"])) {
        if($imageFileType == "pdf") {
            if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file)) {
                $mysqli = conexion\abrirConexion();
                $sql = "UPDATE datosapp SET Test='".$target_file."'";
                $resultado = $mysqli->query($sql);
                header("Location: administrador.php");
            } else {
                echo "Sorry, there was an error uploading your file.";
            }
        } else {
            echo "Sólo se admiten archivos PDF.";
        }
    }
?>

This is the php.ini file

;;;;;;;;;;;;;;;;
; File Uploads ;
;;;;;;;;;;;;;;;;

; Whether to allow HTTP file uploads.
; http://www.php.net/manual/en/ini.core.php#ini.file-uploads
file_uploads = On

; Temporary directory for HTTP uploaded files (will use system default if not
; specified).
; http://www.php.net/manual/en/ini.core.php#ini.upload-tmp-dir
;upload_tmp_dir =

; Maximum allowed size for uploaded files.
; http://www.php.net/manual/en/ini.core.php#ini.upload-max-filesize
upload_max_filesize = 2M

and when I run the form to upload PDF's of less than half a Megabyte, what is printed is: "Sorry, there was an error uploading your file.".

When doing Print_r on $ _FILES I get the following:

 Array ( [fileToUpload] => Array ( [name] => cv.pdf [type] => application/pdf [tmp_name] => /tmp/phpeudTNd [error] => 0 [size] => 154193 ) )