Searching for a value in an array using PHP - php

Question

I have a list of users in my mongodb database, which can then follow each other -pretty standard. Using php I want to check if a specific user is following another user. My data looks like this.
array (
'_id' => ObjectId("56759157e1095db549d63af1"),
'username' => 'Joe',
'following' =>
array (
0 =>
array (
'username' => 'John',
),
1 =>
array (
'username' => 'Tom',
),
),
)
array (
'_id' => ObjectId("56759132e1095de042d63af4"),
'username' => 'Tom',
'following' =>
array (
0 =>
array (
'username' => 'Joe',
),
1 =>
array (
'username' => 'John',
),
2 =>
array (
'username' => 'Sam',
),
),
)
I want a query that will check if Joe is following Sam (which he's not) - so it would produce no results. However, if I was to query the database to check if Tom was following Sam, then it would produce a result to indicate he is (because he is). Do you know how I would do this in PHP? I've experimented with Foreach loops, but I haven't been able to get the results I want.

Answer 1

Make it by DB query, by php it will take more resources
Still if you want by php you can make it so
$following=false;
foreach($data as $v) if ($v['username'] == 'Joe') {
foreach($v['following'] as $v1) if (in_array('Sam', $v1)) {
$following=true;
break 2;
}
}
echo $following;

Answer 2

Such queries are best done in SQL, but if you insist on a PHP-based solution I would suggest to turn the data structure into items keyed by name. Once you have that it is a piece of cake to find relationships:
function organisePersons($data) {
$persons = array();
foreach($data as $person) {
$list = array();
foreach($person["following"] as $following) {
$list[$following["username"]] = $following["username"];
}
$person["following"] = $list;
$person["followedBy"] = array();
$persons[$person["username"]] = $person;
}
// link back to get all "followedBy":
// You can skip this block if you don't need "followedBy":
foreach ($persons as $person) {
foreach($person["following"] as $following) {
echo $person["username"] . " f. $following<br>";
if (!isset($persons[$following])) {
$persons[$following] = array(
"_id" => null, // unknown
"username" => $following,
"following" => array(),
"followedBy" => array()
);
}
$persons[$following]["followedBy"][] = $person["username"];
}
}
// return the new structure
return $persons;
}
So first call the function above with the data you have:
$persons = organisePersons($data);
And then you can write this:
if (isset($persons["Joe"]["following"]["Sam"])) {
echo "Joe is following Sam"; // not in output
};
if (isset($persons["Tom"]["following"]["Sam"])) {
echo "Tom is following Sam"; // in output
};
But also:
echo "Tom is following " . implode($persons["Tom"]["following"], ", ");
// Output: Tom is following Joe, John, Sam
And even the reverse question "Tom is followed by who?":
echo "Tom is followed by " . implode($persons["Tom"]["followedBy"], ", ");
// Output: Tom is followed by Joe