php / mysql数组删除字段

Question

I am running a query on a dbase that returns a multi-field recordset or array on fetch. The array is multi-field as I need several fields to output to the screen. However, I then want to save an array of just one variable, the id for each record. to compare against another list of records. So I need to, in effect, strip all but one field from the array.

In effect, I want to reduce (not using proper array notation):

{1 red dog, 2 orange cat, 3 yellow canary}

to

{1,2,3}

Is there an easy way to do this?

Thanks in advance!

Answer 1

Basically what you want is called array plucking; here's an RFC to introduce this into the language, but it hasn't been accepted.

In the meantime you'd just have to do it the old fashioned way:

$a = array(
    array('id' => 1, 'title' => 'title1'),
    array('id' => 2, 'title' => 'title2'),
);

array_map(function($v) {
    return $v['id'];
}, $a);

// returns array(1, 2)

Before 5.3 you'd have to write it like so:

function getid($v)
{
    return $v['id'];
}

array_map('getid', $a);