Only variables should be passed by reference

Question

// Other variables
$MAX_FILENAME_LENGTH = 260;
$file_name = $_FILES[$upload_name][\'name\'];
//echo \"testing-\".$file_name.\"
\";
//$file_name = strtolower         


        

Answer 1

Assign the result of explode to a variable and pass that variable to end:

$tmp = explode('.', $file_name);
$file_extension = end($tmp);

The problem is, that end requires a reference, because it modifies the internal representation of the array (i.e. it makes the current element pointer point to the last element).

The result of explode('.', $file_name) cannot be turned into a reference. This is a restriction in the PHP language, that probably exists for simplicity reasons.