Move items of an array into the start of a multidimensional array - php

Question

I have an array that contains some other arrays, I will make a sample of the original structure below in order to understand my issue.
$foo = array(
[0] => array('name' => foo, 'offered' => 1)
[1] => array('name' => foo)
[2] => array('name' => foo, 'offered' => 1)
[3] => array('name' => foo, 'offered' => 1)
);
What i want to do is, to sort my array in order to get first every array that contains the key 'offered'. In the example above i need do get this type of order. [0],[2],[3],[1].

Answer 1

You could use uasort() with a custom comparison function.
$foo = array(
array('name' => 'mark', 'offered' => 1),
array('name' => 'joe'),
array('name' => 'bill', 'offered' => 1),
array('name' => 'hugo', 'offered' => 1)
);
uasort($foo, 'customSort');
function customSort($a, $b) {
$a = isset($a['offered']);
$b = isset($b['offered']);
if (($a && $b) || (!$a && !$b)) return 0;
else if ($a && !$b) return -1;
else return 1;
}
print_r($foo);
Please check:
http://php.net/manual/it/function.usort.php
http://php.net/manual/it/function.uasort.php
http://php.net/manual/it/function.uksort.php
Explanation: (a bit simplified for newcomers) When you sort an array with these special sorting functions, you can tell PHP to use a custom function to let it decide whether a value is "less than another" (and return 1) or "greater than" another (and return -1) or "equal to another" (and return 0).
This functions has as parameters ($a, $b) the two array items to compare.
In this case we decide that the ones where "offered" exists are "less than" the others, so they will be sorted first.

Answer 2

I would iterate and check if the key exists, depending on that, rebuild the array.
$final = [];
foreach ($foo as $r) {
if (isset($r['offered']))
array_unshift($final, $r);
else
array_push($final, $r);
}
var_dump($final);

Answer 3

I find the spaceship operator (php7+) to provide a very clean syntax.
Evaluate the offered column from both $a and $b to check if the column is set. If not the isset() false will be treated as 0, otherwise true will be treated as 1.
By writing $b on the left of the operator and $a on the right, DESC sorting is performed -- this positions all 1 (true) evaluations before 0 (false) evaluations.
Code: (Demo)
$array = [
['name' => 'a', 'offered' => 1],
['name' => 'b'],
['name' => 'c', 'offered' => 1],
['name' => 'd', 'offered' => 1],
['name' => 'e']
];
usort($array, function($a, $b) {
return isset($b['offered']) <=> isset($a['offered']);
});
var_export($array);
Output:
array (
0 =>
array (
'name' => 'a',
'offered' => 1,
),
1 =>
array (
'name' => 'c',
'offered' => 1,
),
2 =>
array (
'name' => 'd',
'offered' => 1,
),
3 =>
array (
'name' => 'b',
),
4 =>
array (
'name' => 'e',
),
)