Only variables should be passed by reference

Question

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.

Php 7 compatible proper usage:

$fileName      = 'long.file.name.jpg';
$tmp           = explode('.', $fileName);
$fileExtension = end($tmp);

echo $fileExtension;
// jpg

Everyone else has already given you the reason you're getting an error, but here's the best way to do what you want to do: $file_extension = pathinfo($file_name, PATHINFO_EXTENSION);

save the array from explode() to a variable, and then call end() on this variable:

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

btw: I use this code to get the file extension:

$ext = substr( strrchr($file_name, '.'), 1);

where strrchr extracts the string after the last . and substr cuts off the .

Try this:

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

The reason is that the argument for end is passed by reference, since end modifies the array by advancing its internal pointer to the final element. If you're not passing a variable in, there's nothing for a reference to point to.

See end in the PHP manual for more info.

Since it raise a flag for over 10 years, but works just fine and return the expected value, a little stfu operator is the goodiest bad practice you are all looking for:

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

But warning, don't use in loops due to a performance hit. Newest version of php 7.3+ offer the method array_key_last() and array_key_first().

https://www.php.net/manual/en/function.array-key-last.php

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