文件上载返回“未定义的索引”错误

I'm trying to get the error of my uploaded file but I get the following error :

if(isset($_FILES['fichier']) && $_FILES['fichier']['error'] == 0)
{
        //do stuff here, no problem
}

    //get an error on this line "Notice: Undefined index: fichier in .."
elseif($_FILES['fichier']['error'] != 0)
{

}
else
{
    echo 'no file selected or an error occured with the page.';
}

I need to get the error code (1 to 8)

Your Boolean logic is incorrect, resulting in the elseif block being called when there is no file. Try the following:

if (isset($_FILES['fichier'])) {

    // we know we have a file; do our error checking.
    if ($_FILES['fichier']['error'] == 0) {
        // do stuff here, no problem
    } else {
        // handle the error
    }
} else {
    echo 'no file selected or an error occured with the page.';
}

check if send file with enctype='multipart/form-data' in form sender