Merge child arrays

benwiggy
benwiggy used Ask the Experts™
on
I'm trying to find an elegant way of achieving the following:

- merge the "availability_" elements where the "flight_number" matches
- So that there is only one child array for each flight number (i.e. delete any further child arrays after the merge)
- Note: There won't be an occurrence where there are conflicting "availability_" values for the same flight number
- If no availability_ value is set for a given flight number, set it to 0.

I would like to turn this:

Array
(
    [0] => Array
        (
            [flight_number] => BA0179
            [availability_first] => 
            [availability_business] => 
            [availability_economy] => 99
            [flight_departure] => 2013-10-16 12:40
        )
    [1] => Array
        (
            [flight_number] => BA0213
            [availability_first] => 
            [availability_business] => 
            [availability_economy] => 6
            [flight_departure] => 2013-10-16 13:40
        )
    [2] => Array
        (
            [flight_number] => BA0179
            [availability_first] => 
            [availability_business] => 1
            [availability_economy] => 
            [flight_departure] => 2013-10-16 12:40
        )
)

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into

Array
(
    [0] => Array
        (
            [flight_number] => BA0179
            [availability_first] => 0
            [availability_business] => 1
            [availability_economy] => 99
            [flight_departure] => 2013-10-16 12:40
        )
    [1] => Array
        (
            [flight_number] => BA0213
            [availability_first] => 0
            [availability_business] => 0
            [availability_economy] => 6
            [flight_departure] => 2013-10-16 13:40
        )
)

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Most Valuable Expert 2011
Top Expert 2016

Commented:
I could see using usort() to sort by flight number, then using an iterator like foreach to walk the resulting array.  I'll try to show you a code example in a few minutes.
Most Valuable Expert 2011
Top Expert 2016
Commented:
This looks OK to me.  See http://www.laprbass.com/RAY_temp_benwiggy.php

<?php // RAY_temp_benwiggy.php
error_reporting(E_ALL);
echo '<pre>';

// TEST DATA
$td = Array
(
    '0' => Array
        (   'flight_number' => 'BA0179'
        ,   'availability_first' => ''
        ,   'availability_business' => ''
        ,   'availability_economy' => 99
        ,   'flight_departure' => '2013-10-16 12:40'
        )
,   '1' => Array
        (   'flight_number' => 'BA0213'
        ,   'availability_first' => ''
        ,   'availability_business' => ''
        ,   'availability_economy' => 6
        ,   'flight_departure' => '2013-10-16 13:40'
        )
,   '2' => Array
        (   'flight_number' => 'BA0179'
        ,   'availability_first' => ''
        ,   'availability_business' => 1
        ,   'availability_economy' => ''
        ,   'flight_departure' => '2013-10-16 12:40'
        )
)
;
// DOES IT LOOK RIGHT? (YES)
print_r($td);

// SORT BY FLIGHT NUMBER
function flight_sort($a, $b)
{
    if ($a["flight_number"] == $b["flight_number"]) return 0;
    return ($a["flight_number"] < $b["flight_number"]) ? -1 : 1;
}
usort($td, 'flight_sort');

// CREATE A TEMPLATE WITH ZERO VALUES
$tmp = $td[0];
foreach ($tmp as $key => $val) $tmp[$key] = 0;

// SET UP FOR THE ITERATOR
$sum = $tmp;
$out = array();
$old_flight_number = FALSE;

// ITERATE OVER THE TEST DATA
foreach ($td as $now)
{
    // IF A NEW FLIGHT NUMBER
    if ($now['flight_number'] != $old_flight_number)
    {
        // SAVE THE LAST SUMMARY
        $out[] = $sum;

        // SET A NEW FLIGHT NUMBER
        $old_flight_number = $now['flight_number'];

        // COPY THE TEMPLATE
        $sum = $tmp;
    }

    // WHETHER OR NOT A NEW FLIGHT NUMBER, FILL IN THE PARTS
    foreach ($now as $key => $val)
    {
        if (substr($key,0,1) == 'f') $sum[$key] = $val;
        if (substr($key,0,1) == 'a') $sum[$key] += $val;
    }
}

// APPEND LAST FLIGHT
$out[] = $sum;

// DECLOP THE TEMPLATE
unset($out[0]);

// SHOW THE WORK PRODUCT
print_r($out);

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Best regards, ~Ray
Expert of the Year 2008
Top Expert 2008
Commented:
My suggestion would be to convert the data into:
$flights=Array
(
    [BA0179] => Array
        (
            [availability_first] => 0
            [availability_business] => 1
            [availability_economy] => 99
            [flight_departure] => 2013-10-16 12:40
        )
    [BA0213] => Array
        (
            [availability_first] => 0
            [availability_business] => 0
            [availability_economy] => 6
            [flight_departure] => 2013-10-16 13:40
        )
)

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The advantages of the new structure are:
a. fewer elements - the [flight_number] key no longer exists.  Intead, the actual flight number becomes the top-level key.
b. easier to find/search details for a flight number - ex:
$id='BA0213';
if( isset($flights[$id]) )
{
   //if it makes it here, the flight exists
   print_r($flights[$id]);
}

Try the code below:
$data=Array(
    '0' => Array(
            'flight_number' => 'BA0179'
            ,'availability_first' => NULL
            ,'availability_business' => NULL
            ,'availability_economy' => 99
            ,'flight_departure' => '2013-10-16 12:40'
        )
    ,'1' => Array(
            'flight_number' => 'BA0213'
            ,'availability_first' => NULL
            ,'availability_business' => NULL
            ,'availability_economy' => 6
            ,'flight_departure' => '2013-10-16 13:40'
        )
    ,'2' => Array(
            'flight_number' => 'BA0179'
            ,'availability_first' => NULL
            ,'availability_business' => 1
            ,'availability_economy' => NULL
            ,'flight_departure' => '2013-10-16 12:40'
        )
);

$flights=Array();
foreach($data as $f)
{
	$id=$f['flight_number'];

        //this gets rid of the flight_number key/element
	unset($f['flight_number']);

	$f['availability_first']=(int)$f['availability_first'];
	$f['availability_business']=(int)$f['availability_business'];
	$f['availability_economy']=(int)$f['availability_economy'];

	if(!isset($flights[$id]))
	{
		$flights[$id]=Array();
	}
	else
	{
		$f['availability_first']=max($f['availability_first'],$flights[$id]['availability_first']);
		$f['availability_business']=max($f['availability_business'],$flights[$id]['availability_business']);
		$f['availability_economy']=max($f['availability_economy'],$flights[$id]['availability_economy']);
	}
	$flights[$id]=array_merge($flights[$id], $f);
	
}
unset($data);
echo '<pre>';
print_r($flights);

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Author

Commented:
Thanks for the suggested solutions and feedback. I've realised that the easiest thing to do is use the flight number as the key (as suggested) - this enables me to include the availability counts as I build out the array.

As the suggested solutions helped me solve the problem, will award points.
Most Valuable Expert 2011
Top Expert 2016

Commented:
Thanks for the points and thanks for using EE.  Going forward you might want to think about using object-oriented notation.  It is often more flexible than array notation.  You might also want to think about what happens if you have the same flight number on different days, or with different "legs" and the same flight number.  These factors may influence the data structure.

Best regards, ~Ray

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