Question

I need to write an array in a CSV file where column order must not be changed. But I want to reduce column titles to a length of max 64 chars. To make the question more general, let’s take a simple example :

$array = array(
    'A te' => 'foo A',
    'Q test' => 'foo Q',
    'Z test' => 'foo Z',
);

var_dump($array);

Give :

array (size=3)
  'A te' => string 'foo A' (length=5)
  'Q test' => string 'foo Q' (length=5)
  'Z test' => string 'foo Z' (length=5)

Now, I want to rename the “Q test” key to “Q tes”. If I do :

$swap = $array["Q test"];
unset($array["Q test"]);
$array["Q tes"] = $swap;
var_dump($array);

Displays :

array (size=3)
  'A te' => string 'foo A' (length=5)
  'Z test' => string 'foo Z' (length=5)
  'Q tes' => string 'foo Q' (length=5)

The column’s position changed, that’s not what I was looking for.

I solved my problem by using (here, reducing keys to 5 chars) :

$keys = array_keys($array);
$values = array_values($array);
$count = count($keys);
for ($i = 0; ($i < $count); $i++)
{
   if (mb_strlen($keys[$i]) > 5)
   {
      $keys[$i] = mb_substr($keys[$i], 0, 5);
   }
}
$array = array_combine($keys, $values);

var_dump($array);

Outputs:

array (size=3)
  'A te' => string 'foo A' (length=5)
  'Q tes' => string 'foo Q' (length=5)
  'Z tes' => string 'foo Z' (length=5)

But this looks very resources-devour… I do need to execute such a code on each of my rows, and I have from 10k to 100k rows.

Is there a simpler way to rename array keys without moving them?

Answer 1

Try this, which should be simpler,

foreach($array as $k=>$v){
   if($k=='Q test'){
      $new_arr['Q tes'] = $array['Q test'];
   }else{
      $new_arr[$k] = $v;
   }
}

print_r($new_arr); //set $array = $new_arr;  to overwrite all values