Unset an array element inside a foreach loop [duplicate]

问题

I'm accessing an array by reference inside a foreach loop, but the unset() function doesn't seem to be working:

foreach ( $this->result['list'] as &$row ) {
    if ($this_row_is_boring) {
        unset($row);
    }
}

print_r($this->result['list']); // Includes rows I thought I unset

Ideas? Thanks!

回答1:

You're unsetting the reference (breaking the reference). You'd need to unset based on a key:

foreach ($this->result['list'] as $key => &$row) {
    if ($this_row_is_boring) {
        unset($this->result['list'][$key]);
    }
}

回答2:

foreach ($this->result['list'] as $key => &$row) {
    if ($this_row_is_boring) {
        unset($this->result['list'][$key]);
    }
}
unset($row);

Remember: if you are using a foreach with a reference, you should use unset to dereference so that foreach doesn't copy the next one on top of it. More info

回答3:

A bit of an explanation to the answers above.

After unset($row) the variable $row is unset. That does not mean the data in $row is removed; the list also has an element pointing to $row.

It helps to think of variables as labels. A piece of data can have one or more labels, and unset removes that label but does not touch the actual data. If all labels are removed the data is automatically deleted.

来源：https://stackoverflow.com/questions/3054886/unset-an-array-element-inside-a-foreach-loop

标签

php

arrays

reference

foreach

unset