Question: I have csv[ ][ ]. How do I use a for each loop to unset data in rows?

```
for each ($index) {
if (conditions to meet) { 
unset(csv[$index]);     
}
}

```

Answer: 
Try this : 

```
foreach ($csv as $key => $value) {
        unset($csv[$key]);
    }

```
<http://docs.php.net/manual/en/control-structures.foreach.php> says:

> In order to be able to directly modify array elements within the loop precede $value with &. In that case the value will be assigned by [reference](http://docs.php.net/manual/en/language.references.php). 

That's what you should use to modify single elements of the rows when using two foreach loops.

```
<?php
$csv = [
    [1,2,3,4,5],
    [2,3,4,5,6],
    [3,4,5,6,7],
    [4,5,6,7,8],
];

// make $row a reference
// so that unset($row[...]) affects $csv and not only a "copy".
foreach( $csv as &$row ) { 
    foreach( $row as $key=>$column ) {
        if ( 0===$column%2 ) { // e.g. remove all even elements
            unset( $row[$key] );
        }
    }
}

var_export($csv);

```

prints

```
array (
  0 => 
  array (
    0 => 1,
    2 => 3,
    4 => 5,
  ),
  1 => 
  array (
    1 => 3,
    3 => 5,
  ),
  2 => 
  array (
    0 => 3,
    2 => 5,
    4 => 7,
  ),
  3 => 
  array (
    1 => 5,
    3 => 7,
  ),
)

```

Or (same output) without foreach loops.

```
<?php
$csv = [
    [1,2,3,4,5],
    [2,3,4,5,6],
    [3,4,5,6,7],
    [4,5,6,7,8],
];

$csv = array_map(
    function($row) {
        return array_filter(
            $row,
            function($col) {
                return 0!==$col%2; 
            }
        );
    },
    $csv
);

var_export($csv);

```