PHP Array how to make it so that all arrays will have the same length

Question

I have a multidimensional array. The arrays will have different lengths and seldom will they have the same length. My problem here is how can I make it so that the arrays will all share the length of the array with the biggest size?

My Array:

Array
(
    [1] => Array
        (
            [Session 2] => Beer
            [Food] => Chicken
            [Drink] => Beer
        )

    [2] => Array
        (
            [Session 2] => Tea
            [Food] => Aaaa
            [Drink] => Ddd
            [Cake] => Weee
            [Brownies] => Rrrr
        )

)

Expected output:

Array
(
    [1] => Array
        (
            [Session 2] => Beer
            [Food] => Chicken
            [Drink] => Beer
            [Cake] => ''
            [Brownies] => ''
        )

    [2] => Array
        (
            [Session 2] => Tea
            [Food] => Aaaa
            [Drink] => Ddd
            [Cake] => Weee
            [Brownies] => Rrrr
        )

)

The array size is not limited to only two arrays. Is this even possible and if so how?

I only want to copy the array keys and not the values its main purpose here is for presenting the content of the array in a table.

I suspect an object would be a better fit - you can define the properties then. — CD001
– CD001, Commented Nov 13, 2018 at 9:29

scrowler · Accepted Answer · 2018-11-13 09:30:29Z

6

Here's one option, where you build an array of all possible array keys, then loop over your original array and set empty strings to the keys that don't exist yet:

// find all possible keys
$keys = [];
foreach ($array as $entry) {
    $keys = array_merge($keys, array_keys($entry));
}

// pad missing keys with an empty string
foreach ($array as &$entry) {
    foreach ($keys as $key) {
        if (!isset($entry[$key])) {
            $entry[$key] = '';
        }
    }
}

answered Nov 13, 2018 at 9:30

scrowler

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6 Comments

Andreas Over a year ago

You don't need the inner loop + the if(). Use array_replace(keys, entry)

scrowler Over a year ago

@Andreas good point - $keys = ['Foo' => '']; then $entry = array_replace($entry, $keys)

magicianiam Over a year ago

thank you. will give this a try but what does this line mean? foreach ($array as &$entry) { the &$entry

Sam Over a year ago

I generally try to avoid modify by reference in loops because of the weird way PHP handles references. Even though it's a bit slower, array_walk() accomplishes the same thing without the possibility of weird side effects.

Diogo Santo Over a year ago

Is it not preferable to also use array_fill_keys to just set all the values to the desired ones? So if he wishes to have all the keys and empty values to just do it as $emptyValuesArray = array_fill_keys(array_keys($targetArray), ''); And avoid the for loops

|

mickmackusa · Accepted Answer · 2022-05-14 00:35:46Z

1

If the main purpose is to show the data in a table, then you do not need to fill in the missing keys. You can use the isset() or empty() functions to determine whether an array has a given key. So, your table code could look like the following:

<?php
foreach ($rows as $row) {
    echo "<tr>";
    echo "<td>" . (isset($row["Session 2"]) ? $row["Session 2"] : "") . "</td>"; //Old school
    echo "<td>" . ($row["Food"] ?? "") . "</td>"; //PHP 7+
    //remaining rows
    echo "</tr>";
}

edited May 14, 2022 at 0:35

mickmackusa♦

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answered Nov 13, 2018 at 9:31

Sam

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2 Comments

Karsten Koop Over a year ago

The null coalescing operator could also be used here

Sam Over a year ago

@KarstenKoop Thanks, I've updated my answer with some better examples

scrowler · Accepted Answer · 2018-11-13 09:44:06Z

0

Let's say the array you're talking about is inside a variable $array,

Do this to find the maximum length;

$max = 0;

foreach($array as $index => $value){

    if($index == sizeof($array) - 1){
        break;
    }

    if($index && $max > sizeof($array[$index+1])){
        $max = $max;
    }
    if(!$index && sizeof($value) > sizeof($array[$index+1])){
        $max = sizeof($value);
    }else {
        $max = sizeof($array[$index+1]);
    }
}

edited Nov 13, 2018 at 9:44

scrowler

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answered Nov 13, 2018 at 9:41

Matnex Mix

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