Sort a multi-dimensional array on two subarray values - php

Question

I would like to sort an array on eta ASC then ab ASC.
Here's the input array:
$res_ubr=array(
"0"=>array(
"ab"=>"jdfd",
"bb"=>"iweuiru",
"eta"=>4
),
"1"=>array(
"ab"=>"dsdjdfd",
"bb"=>"iuiru",
"eta"=>5
),
"2"=>array(
"ab"=>"jdgfd",
"bb"=>"edfguiru",
"eta"=>2
),
"3"=>array(
"ab"=>"err",
"bb"=>"iuierru",
"eta"=>2
),
"4"=>array(
"ab"=>"fdfdf",
"bb"=>"dfdf",
"eta"=>3
)
);
Here is my expected result:
[
['ab'=>'err', 'bb'=>'iuierru', 'eta'=>2],
['ab'=>'jdgfd', 'bb'=>'edfguiru', 'eta'=>2],
['ab'=>'fdfdf', 'bb'=>'dfdf', 'eta'=>3],
['ab'=>'jdfd', 'bb'=>'iweuiru', 'eta'=>4],
['ab'=>'dsdjdfd', 'bb'=>'iuiru', 'eta'=>5]
]
This is what I've tried:
$res2=$res_ubr;
$temp=array();
foreach($res_ubr as $key=>$val){
foreach($res2 as $k=>$v){
if($val['eta']>$v['eta']){
$temp[]=$res_ubr[$key];
$res_ubr[$key] =$res_ubr[$k];
$res_ubr[$k]=$temp[];
}
}
}
print_r($res_ubr);
For context, the eta value is the time in minutes that the cab is expected to arrive.

Answer 1

You only need to assign a unique temporary key. There are two eta's with a value of 2 in your input array, so you will need to provide a "tie breaker". I am using the ab value to dictate the sorting order when two duplicate etas exist. I'm arbitrarily padding the eta values to an 8 digit number to ensure that numeric sorting occurs as intended. Without left padding with zeros, 10 would come before 2 because the temporary keys will be sorted as strings (one character at a time from left to right) and 1 comes before 2.
foreach($res_ubr as $sub){
$result[str_pad($sub["eta"],8,'0',STR_PAD_LEFT).$sub["ab"]]=$sub;
}
ksort($result);
var_export(array_values($result));
Because you say the eta are taxi arrival times, I'd bet your business that no eta is going to be in the tens of millions of minutes, so you can reduce the padding amount from 8 down to what ever is reasonably expected.
Keep in mind that if there is ever a duplicate temporary key (a matching pair of eta & ab), then my method will overwrite the first element with the second and you will have missing data. If this is a remote possibility, you should also append bb to the temporary key. If this, again, at risk of being a duplicate, you should add a randomly generated string of numbers to prevent your data being erased.
Output with eta ASC, ab ASC:
array (
0 =>
array (
'ab' => 'err',
'bb' => 'iuierru',
'eta' => 2,
),
1 =>
array (
'ab' => 'jdgfd',
'bb' => 'edfguiru',
'eta' => 2,
),
2 =>
array (
'ab' => 'fdfdf',
'bb' => 'dfdf',
'eta' => 3,
),
3 =>
array (
'ab' => 'jdfd',
'bb' => 'iweuiru',
'eta' => 4,
),
4 =>
array (
'ab' => 'dsdjdfd',
'bb' => 'iuiru',
'eta' => 5,
),
)