# Processing Multiple Arrays Together
array_merge overwrites the values of the first array with the values of the second array, if it cannot renumber the index.
You can use the + operator to merge two arrays in a way that the values of the first array never get overwritten, but it does not renumber numeric indexes, so you lose values of arrays that have an index that is also used in the first array.
# Array intersection
The array_intersect function will return an array of values that exist in all arrays that were passed to this function.
Array keys are preserved. Indexes from the original arrays are not.
array_intersect only check the values of the arrays. array_intersect_assoc function will return intersection of arrays with keys.
array_intersect_key function only check the intersection of keys. It will returns keys exist in all arrays.
# Changing a multidimensional array to associative array
If you have a multidimensional array like this:
And you want to change it to an associative array like this:
You can use this code:
Or, you can skip setting $associativeArrayKeys and $associativeArrayValues and use this simple one liner:
# Combining two arrays (keys from one, values from another)
The following example shows how to merge two arrays into one associative array, where the key values will be the items of the first array, and the values will be from the second:
PHP array_merge
Summary: in this tutorial, you will learn how to use the PHP array_merge() function to merge one or more arrays into one.
Introduction to the PHP array_merge() function
To merge one or more array into an array, you use the array_merge() function:
The array_merge() function accepts one or more arrays and returns a new array that contains the elements from the input arrays.
The array_merge() function appends the elements of the next array to the last element of the previous one.
When the elements in the input arrays have the string keys, the later value for that key will overwrite the previous one.
However, if the array_merge() function will not overwrite the values with the same numeric keys. Instead, it renumbers the numeric keys starting from zero in the result array.
Starting from PHP 7.4.0, you can call the array_merge() function without any arguments. In this case, the function will return an empty array.
PHP array_merge() function examples
Let’s take some examples of using the array_merge() function.
1) Simple array_merge() function example
The following example uses the array_merge() function to merge two arrays into one:
- First, define two indexed arrays: $server_side and $client_side .
- Second, merge the $server_side and $client_side arrays into one array using the array_merge() function.
- Third, show the result array.
As you can see clearly from the output, the array_merge() function renumbers the numeric keys of the elements in the result array.
2) Using array_merge() function with string keys
The following example uses the array_merge() function with the array with the string keys:
Because both $before and $after arrays have the same elements with the same string keys PHP and JavaScript , the elements in the $before array overwrites the ones in the $after array.
array_merge
Сливает элементы одного или большего количества массивов таким образом, что значения одного массива присоединяются к концу предыдущего. Результатом работы функции является новый массив.
Если входные массивы имеют одинаковые строковые ключи, тогда каждое последующее значение будет заменять предыдущее. Однако, если массивы имеют одинаковые числовые ключи, значение, упомянутое последним, не заменит исходное значение, а будет добавлено в конец массива.
В результирующем массиве значения исходного массива с числовыми ключами будут перенумерованы в возрастающем порядке, начиная с нуля.
How can I merge PHP arrays?
That was my first thought but it doesn’t quite work — however array_merge_recursive might work — too lazy to check right now.
This does what Erik suggested (id no. as array key) and merges vlaues in $array2 to $results .
First off, why don’t you use the ID as the index (or key, in the mapping-style array that php arrays are imo)?
after that you’ll have to foreach through one array, performing array_merge on the items of the other:
Something like that at least. Perhaps there’s a better solution?
I’ve already looked at that and didn’t see how it can help merge multidimensional arrays. Maybe you could give an example.
That is probably what I will need to do as I think the code below will be very slow. The actual code is a bit different because I’m using ADOdb (and ODBC for the other query) but I’ll make it work and post my own answer.
This works, however I think it will be very slow as it goes through the second loop every time: