Question

I have a very little piece of code for testing an array_walk test.

I thought that I could do the same with foreach but then when I pass the value it doesn’t get modified:

<?php
$frutas = [ "d" => "limón", "a" => "naranja", "b" => "banana", "c" => "manzana" ];

function test_alter(&$elemento)
{
  $elemento = "prefijo: $elemento";
  echo "$elemento <br>";
}

foreach($frutas as $clave => $valor) {
  test_alter($valor, $clave);
}
print_r( $frutas ); 
?>

Which outputs:

prefijo: limón
prefijo: naranja
prefijo: banana
prefijo: manzana
Array ( [d] => limón [a] => naranja [b] => banana [c] => manzana ) 

Obviously not modifying array value although its passed by reference.

Answer 1

You are passing $valor to the function … foreach values are not ‘referenced’ values, so you are altering a temporary value, not the actual array value …

try this in your foreach loop:

test_alter($frutas[$clave]);

or, you could:

foreach($frutas as $clave => &$valor){
    test_alter($valor, $clave);
}