How to write a variable in the array - php

Question

I try to write a string into a variable in between an array
if ($row_klasse['RabKlNummerVK'] != ''){
$headerrabklasse = '\'Rabatt\'\=\>\'price\'\,';
}
else {$headerrabklasse = '';}
then I want to write the variable $headerrabklasse in:
$writer = new XLSXWriter();
$writer->writeSheetHeader (Preisliste, array(
'Marke'=>'string',
'Range'=>'string',
'Artikelnummer'=>'string',
'Bezeichnung'=>'string',
'EAN'=>'string',
'kg netto'=>'zahl3',
'VE'=>'string',
'Steuer'=>'string',
'Listenpreis'=>'euro',
$headerrabklasse
'Nettopreis'=>'price3',
'UVP'=>'price'),
['auto_filter'=>true, 'widths'=>[20,50,15,45,15,8,8,8,8,8],
'font-style'=>'bold', 'fill'=>'#eee',
'freeze_rows'=>1,
'freeze_columns'=>0] );
And I always get an error...
HAs anybody an idea?

Answer 1

In PHP you can easily append data to array like this:
//Define array with default values
//BTW: if you work with PHP >= 5.4 better to use [] instead of array()
$sheetHeaders = array(
'Marke'=>'string',
'Range'=>'string',
'Artikelnummer'=>'string',
'Bezeichnung'=>'string',
'EAN'=>'string',
'kg netto'=>'zahl3',
'VE'=>'string',
'Steuer'=>'string',
'Listenpreis'=>'euro',
'Nettopreis'=>'price3',
'UVP'=>'price'
);
if ($row_klasse['RabKlNummerVK'] != ''){
//Here you append data to existing array in format: array[key] = value
$sheetHeaders['Rabatt'] = 'price';
}
//Then use fulfilled array as you want
$writer->writeSheetHeader ($preisliste, $sheetHeaders);

Answer 2

Your array takes keys and values, so you need to write a key name, and pass the variable as a value. I also noticed you were mixing Array declarations. In PHP you can call an array like this:
Array(el1, el2, ...)
or like this:
[el1, el1, ...]
Either one is fine, but for best practices you want to pick one and stick with it.
$writer->writeSheetHeader(Preisliste, [
'Marke'=>'string',
...
'MyNewKeyName' => $headerrabklasse,
...
],
[
...
]
);

Answer 3

I guess you wan't to do this one:
if ($row_klasse['RabKlNummerVK'] != '') {
$headerrabklasse = ['Rabatt' => 'price'];
}
else {$headerrabklasse = [];}
You could do stuff like that:
$writer->writeSheetHeader (Preisliste, array_merge(array(
'Marke'=>'string',
'Range'=>'string',
'Artikelnummer'=>'string',
'Bezeichnung'=>'string',
'EAN'=>'string',
'kg netto'=>'zahl3',
'VE'=>'string',
'Steuer'=>'string',
'Listenpreis'=>'euro',
'Nettopreis'=>'price3',
'UVP'=>'price'),
['auto_filter'=>true, 'widths'=>[20,50,15,45,15,8,8,8,8,8],
'font-style'=>'bold', 'fill'=>'#eee',
'freeze_rows'=>1,
'freeze_columns'=>0]), $headerrabklasse);