Undefined offset Error when searching Array - php

Question

I am searching an array for a known value wid to get the key which will then help me get the cid value.
$proximity = array(
'0' => array ('wid' => 4, 'cid' => 100),
'1' => array ('wid' => 1, 'cid' => 50),
'3' => array ('wid' => 2, 'cid' => 50)
);
$key = array_search(2, array_column($proximity, 'wid'));
print_r($key);
print_r($proximity[$key]['cid']);
When I search for wid 4 and 1 everything works great.
However when I search for wid: 2 I get Undefined offset: 2.
Why is this happening and how do I fix it?

Answer 1

Array_column returns values of field as usual indexed array, even if source array is associative. So the returned key is correct only when source array has no omitted indexes, and your search, in fact, gets "position" in array.
For example, for such an array
$proximity = array(
'a' => array ('wid' => 4, 'cid' => 100),
'b' => array ('wid' => 1, 'cid' => 50),
'c' => array ('wid' => 2, 'cid' => 50)
);
array_column will return
Array
(
[0] => 4
[1] => 1
[2] => 2
)
If you really want to search through array_column, to work around this problem and get item by that "position", use
print_r(array_slice($proximity, $key, 1)['cid']);
or
print_r(array_values($proximity)[$key]['cid']);

Answer 2

It's because when you are doing array_search() it is only searching the first level of the array, you can search like the following:
<?php
echo 'hello world';
$proximity = array(
'0' => array ('wid' => 4, 'cid' => 100),
'1' => array ('wid' => 1, 'cid' => 50),
'3' => array ('wid' => 2, 'cid' => 50)
);
foreach($proximity as $subarray){
$key = array_search(2, array_column($subarray, 'wid'));
echo print_r($key) . '<br />';
echo print_r($proximity[$key]['cid']) . '<br />';
}
?>
This searches each sub array that is in the main array, meaning it doesn't matter how many elements are in $proximity, it will search all of them.

Answer 3

array_column() is trashing your original keys. I don't think there is any shame in using a loop with a break. This is clean and fast and the gaps in the keys are no bother; in fact your original keys are preserved if you need them.
Code: (demo: https://3v4l.org/8XWcf )
$proximity = array(
'0' => array ('wid' => 4, 'cid' => 100),
'1' => array ('wid' => 1, 'cid' => 50),
'3' => array ('wid' => 2, 'cid' => 50)
);
$wid=2;
foreach($proximity as $i=>$a){
if($a['wid']==$wid){
echo "i=$i and cid={$a['cid']}";
break;
}
}
Output:
i=3 and cid=50
If you don't want control structures as iterators, this seems like a sensible alternative:
$wid=2;
$proximity=array_column($proximity,NULL,'wid');
if(isset($proximity[$wid])){
echo "cid={$proximity[$wid]['cid']}";
}else{
echo 'wid not found';
}
This assumes wid values are unique and uses the values as keys for the subarrays. Demo : https://3v4l.org/Ph1tH