PHP Merge 2 arrays if value is found and create new value - php

Question

i want to compare 2 arrays. If a value from $a ist found is $b there should be make a new value in $a like [found] => true.
Array $a:
Array
(
[1] => Array
(
[grpID] => 1
[groupname] => Marketing
)
[2] => Array
(
[grpID] => 2
[groupname] => Vertrieb
)
[4] => Array
(
[grpID] => 4
[groupname] => Produktion
)
)
Array $b:
Array
(
[1] => Array
(
[usrID] => 23
[grpID] => 1
)
)
So now i want to compare these two.
The result should look like the following, because $b[1]['grpID'] was like in $a[1]['grpID']:
Array $c (or $a as manipulated?):
Array
(
[1] => Array
(
[grpID] => 1
[groupname] => Marketing
[found] => true
)
[2] => Array
(
[grpID] => 2
[groupname] => Vertrieb
[found] => false
)
)
The size of $b may vary so i don't think i can work with a for-loop, can i?
Sorry, i've got no code so far as i don't have an idea how to start.
Thanks in advance.
Best regards

Answer 1

Do it with an temporary array $temp.
$a = array();
$b = array();
$c = array();
$tmp = array();
$a[1] = array('grpID' => 1, 'groupname' => 'Marketing');
$a[2] = array('grpID' => 2, 'groupname' => 'Vertrieb');
$a[4] = array('grpID' => 4, 'groupname' => 'Produktion');
$b[1] = array('usrID' => 23, 'grpID' => 1);
foreach ($b as $key => $value) {
$tmp[] = $value['grpID'];
}
foreach ($a as $key => $value) {
$c[] = array_merge($value, array('found' => (in_array($value['grpID'], $tmp) ? 'true' : false)));
}

Answer 2

Checkout the following code
<?php
$a = array(
array(
'grpID' => 1,
'groupname' => 'Marketing'
),
array(
'grpID' => 2,
'groupname' => 'Vertrieb'
),
array(
'grpID' => 5,
'groupname' => 'Produktion'
)
);
$b = array(
array(
'grpID' => 1,
'usrID' => 23
)
);
$c = array();
for ($i = 0; $i < count($a); $i++)
{
$tmp = $a[$i];
$tmp['found'] = FALSE;
for ($j = 0; $j < count($b); $j++)
{
if ($tmp['grpID'] === $b[$j]['grpID'])
{
$tmp['found'] = TRUE;
break;
}
}
array_push($c, $tmp);
}
// Final output
print_r($c);
?>

Answer 3

There are a few different ways to do this, I toyed with the idea of using array_walk and using a object orientated approach. The way below is the simplest to implement but if I were doing this on a system of my own I would probably go object orientated for cleaner code and better maintenance.
here are the help pages for array_walk http://uk1.php.net/array_walk just in case you wanted to look at another way.
$foundGroups = array();
//set all found values to false
foreach ($a as $group) {
$group['found'] = false;
}
foreach ($b as $user) {
$groupToFind = $user['grpID'];
// This is to limit the number of times we do this, there is no point
// in looking for the same group twice
if (!in_array($groupToFind, $foundGroups)) {
foreach ($a as $group) {
if ($group['grpID'] == $groupToFind) {
$group['found'] = 'true';
$foundGroups[] = $groupToFind;
}
}
}
}