Array joining using an id as reference - php

Question

I have 2 tables. The first table is an equipment table. A query from this table looks like this:
id name user_id
-----------------------
1 equip1 1001
2 equip2 1002
The seconde table is an users table. A query from this table looks like this:
id username
--------------
1001 user1
1002 user2
I want to achieve something like this:
id name user_id username
-----------------------------------
1 equip1 1001 user1
2 equip2 1002 user2
Is there a way to join both arrays like doing a join query? I can't use JOIN in my query, because the tables are on different databases (I know there is a way to do JOIN on different databases, but I'm not allowed to use that).
EDIT:
I'm adding the structure of these arrays.
$equipment = array(
[0] => array(
['id'] => 1,
['name'] => 'equip1',
['user_id'] => 1001
),
[1] => array(
['id'] => 2,
['name'] => 'equip2',
['user_id'] => 1002
)
);
$users= array(
[0] => array(
['id'] => 1001,
['username'] => 'user1'
),
[1] => array(
['id'] => 1002,
['username'] => 'user2'
)
);

Answer 1

You would likely have to join the queries yourself. I don't believe there is a built in function (not counting walk or map with a callback). This is what I would do
//empty array for indexing users under their id for faster loopups
$users = array();
//loop over the users result
foreach($usersResult as $row){
//index users under their id.
$users[$row['id']] = $row['username'];
}
//now loop over the equipment to join the arrays together
foreach($equipmentResult as $key=>$row){
//add the username column
$row['username'] = isset($users[$row['user_id']])?$users[$row['user_id']]:null;
//save back into the equipment row
$equipmentResult[$key] = $row;
}
//display
print_r($equipmentResult);
This could easily be turned into a function where you pass arguments that would build the "ON" portion for the column names.
Edit: Made it a function.
<?php
/**
* Joins two arrays as if they were joined in a query
* #param Array $arrayA The base (left) array to join into
* #param Array $arrayB The right array to join into A
* #param String $colA The column name to join on for arrayA
* #param String $colB [optional] The column name to join on for arrayB. If
* blank, then it is assumed the same column name as colA
* #param boolean $leftJoin [optional] Should this be a left join and include rows
* from A where no value exists in B?
* #return void
*/
function array_join($arrayA, $arrayB, $colA, $colB=null, $leftJoin=false){
//if no value was passed for colB, assume it is the same value as colA
if(is_null($colB)){
$colB = $colA;
}
//output data
$out = array();
//create an index for array B for faster lookups
$idxB = array();
$colsB = array();
foreach($arrayB as $row){
//get the value from B
$valB = $row[$colB];
//if the column doesn't exist in the index, add it
if(!isset($idxB[$colB])){
$idxB[$colB] = array();
}
//index the value
$idxB[$valB][] = $row;
//store the known column to an array for use below
if(empty($colsB)){
$colsB = array_keys($row);
}
}
//loop over array A
foreach($arrayA as $rowA){
//get the value for the column
$valA = $rowA[$colA];
//does the value from A exist in B
$rowB = isset($idxB[$valA])?$idxB[$valA]:null;
//join the rows
//add blank columns if left join
if($leftJoin && is_null($rowB)){
$rowBJoin = array_combine($colsB, array_fill(0, count($colsB), null));
//add the row to our output
$out[] = $rowA + $rowBJoin;
} else {
//inner join or value is not null
//loop over all the rows from the B index that we are joining on
foreach($rowB as $rowBJoin){
//add the row to our output
$out[] = $rowA + $rowBJoin;
}
}
}
return $out;
}