PHP Unsetting data in an array

Question

I have the following line which reads a csv and turns each row into an Array

$reader = new CSV\CSVReader('somecsv.csv');

So if I then do

while ($row = $reader->getRow()) {
    print "<pre>";
    print_r($row);
    print "</pre>";
}

It outputs data like so

Array
(
    [Column1] => some
    [Column2] => data
    [Column3] => hi
    [Column4] => wow
    [Column5] => help
)
Array ...

Say I wanted to remove column1, inside the while loop I can place

unset($row['column1']);

And this will remove column1 from the output. However, if I place a function in my $reader class like so

public function unsetColumns($row)
{
    unset($row['column1']);
}

And I change my while loop to the following

while ($row = $reader->getRow()) {
    $reader->unsetColumns($row);  //this does not work
    unset($row['column1']);  //this works
    print "<pre>";
    print_r($row);
    print "</pre>";
}

Then the function call does not remove the column, but the unset does. I dont have both in there at the same time, just put them both there so you can see what works and what does not.

Why would this be?

Thanks

Answer 1

You can pass your array by reference read here more on Passing by Reference

public function unsetColumns(&$row)
{
    unset($row['column1']);
}

while ($row = $reader->getRow()) {
    $reader->unsetColumns($row);  //this does not work
    unset($row['column1']);  //this works
    print "<pre>";
    print_r($row);
    print "</pre>";
}

Answer 2

You are just passing $row, it is getting deleted in function call also.

But, you are not returning it (neither you are passing reference to $row).

Do two changes:

$row = $reader->unsetColumns($row);

And

public function unsetColumns($row)
{
    unset($row['column1']);
    return $row;
}

So, that your column deletion activity gets used.

Answer 3

You can pass the current $row by reference it to manipulate inside a function and also see those changes outside of that functions scope.

<?php
public function unsetColumns( &$row )
{
    unset( $row['column1'] );
}

while( $row = $reader->getRow() ) {
    $reader->unsetColumns( $row );

    print "<pre>";
    print_r($row);
    print "</pre>";
}

The difference to your existing code is the additional ampersand in front of the arguments name: &$row in the function declaration.

See: http://php.net/manual/en/language.references.pass.php