Simple way to replace value in array in PHP when you know the index

Question

I have created an array in PHP of strings. While my understanding of PHP is imperfect, I believe that arrays are by default ordered by an index and I should be able to access an element of the array using: array[0] or array[1] etc. Regardless, I have created the array by explicitly creating an index with the following code employing a loop:

//create empty array container
    $myarray = "";
//create counter
    $i = 0;
//begin loop of limited size...
    $myarray[$i] = "some color...this changes with each iteration of loop";
    $i = $i + 1;
    //end loop

Note I end up with something like 1=>red,2+>blue,3+>green etc.

I know this code works because it creates an array that if I implode, gives me the string that I want e.g. redbluegreen

$arrayasstring = implode("",$myarray);//produces redbluegreen

However, I would like to access one of the values of the loop using the index and change it. For example, I might want to change $array[0] from red to purple.

 $index = 0;
    $myarray[$index] = "purple"; //does not work

What is a simple way to accomplish this?

Thanks for any suggestions.

That should work. What's the difference from your original code in the loop? — Barmar
– Barmar, Commented Aug 4, 2021 at 16:19
Your loop is modifying $myarray, but then you use $array in the call to implode(). — Barmar
– Barmar, Commented Aug 4, 2021 at 16:20
All these snippets with different variables are confusing, it's hard to tell what you're doing wrong. Please post a minimal reproducible example. — Barmar
– Barmar, Commented Aug 4, 2021 at 16:21
I corrected the myarray vs. array conflict which was a typo. — Arjun321
– Arjun321, Commented Aug 4, 2021 at 20:16

Alexandro Giles · Accepted Answer · 2021-08-04 16:44:00Z

1

To initialize an Array you have to use [] or the function array:

In your example:

$myarray = array();

If you want to add a series of values with the default key assignment you only have to put in between the parenthesis: array(color1, color2, color3)

$myarray = array('blue', 'red', 'yellow')

Then you can view what is on your variable, using: print_r($myarray)

print_r($myarray)
// this will output:
Array
(
    [0] => blue
    [1] => red
    [2] => yellow
)

After this, now you can change the key => value, as you want:

$index = 0;
$myarray[$index] = "purple";
print_r($myarray);

//this will now output:
Array
(
    [0] => purple
    [1] => red
    [2] => yellow
)

And your job is done.

Observations:

In your question, you are using two differents arrays: $myarray and $array, you are having an error because $array[$index] is different to the first $myarray[$i] = "some color...this changes with each iteration of loop";
Use print_r($yourVariable) to show what is in the variable to debug what you are doing wrong.

answered Aug 4, 2021 at 16:44

Alexandro Giles

4925 silver badges19 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Arjun321 Over a year ago

Not initializing array properly may have been the main issue. Also I was using var_dump which just shows string and number of characters instead of print_r. Using print_r helped me to debug.

Alexandro Giles Over a year ago

Using $myarray = array('blue', 'red', 'yellow'); you don't need to initialize the array, since you are creating it with values. There's another way that you can initialize it: $myArray = []; $myArray = array(); $myArray = (array) null;

Collectives™ on Stack Overflow

Simple way to replace value in array in PHP when you know the index

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related