错误：第一个参数应该是一个数组

I have this code and no code before it that refers to any variables seen below. Yet I still can't find why I'm getting the error: "First argument should be an array in..."

$array = array("element here for reason");

function sortdata()
{
    $File = fopen("Names.txt", "r");

    //put each file line into an array element
    while(!feof($File))
    {
        array_push($array, fgets($File));
    }
}

$array is out of scope to the function. You can bring it into scope using global.

$array = ..;
function sortdata() {
    global $array;
    ...
}
sortdata();

Alternatively, you can pass it by reference into the function.

$array = ..;
function sortdata(&$array) {
    ...
}
sortdata($array);

You should try to first initialize the array and bring the array within the scope of the function like so:

$array = array();
array_push($array, "element here for reason");

function sortdata()
{
    global $array;

    $File = fopen("Names.txt", "r");

    //put each file line into an array element
    while(!feof($File))
    {
        array_push($array, fgets($File));
    }
}

The issue with the code is that you are not passing the $array variable into the function. Aside from that, it would be more efficient to use the shortcut way to add an item to the array instead of calling array_push since it eliminates the overhead of calling a function.

$array = array("element here for reason");

function sortdata($array)
{
    $File = fopen("Names.txt", "r");

    //put each file line into an array element
    while(!feof($File))
    {
        $array[] = fgets($File);
    }

    return $array;
}

You use variable $array inside function body. In this case this is local variable and it automatically sets to string.

For work with your global variable $array you should use instruction global in your function.

function sortdata() {
global $array;
/* there your code for work with $array */
}

This give you backward compatibility

function sortdata(array $array = array())
{
    $File = fopen("Names.txt", "r");

    while(!feof($File))
    {
      array_push($array, fgets($File));
    }


    return $array;
}