mt_rand() returns unexpected output - php

Question

I am working with my ad system of my site and having trouble with this.
<?php
function bdads($size, $company) {
if($company == 'nufa') {
if ($size == '300'){
echo 'n300';
}
if ($size == '160'){
echo 'n160';
}
if ($size == '728'){
echo 'n728';
}
if ($size == '700'){
echo 'n700';
}
}
if($company == 'gnr') {
if ($size == '300'){
echo 'g300';
}
if ($size == '160'){
echo 'g160';
}
if ($size == '728'){
echo 'g728';
}
if ($size == '700'){
echo 'g700';
}
}
}
function bdad($size, $company){
$zsize = $size;
if($company == 'nufa'){
echo bdads($zsize, 'nufa');
}
if($company == 'gnr'){
echo bdads($zsize, 'gnr');
}
if($company == 'both'){
$RandomList = [ bdads($zsize, 'gnr'), bdads($zsize, 'nufa')];
echo $RandomList[mt_rand(0, count($RandomList) - 1)];
}
}
?>
Now, Everything seems fine.. as example,
<?php echo bdad(728, 'gnr'); ?>
returning g728 (as expected)
<?php echo bdad(300, 'nufa'); ?>
returning n300 (as expected)
But all trouble is in generating random content.
<?php echo bdad(300, 'both'); ?>
returning g300n300
I want it to choose either g300 or n300 randomly.
EDIT:
Changed $a to $RandomList, but still same result

Answer 1

I tried to simplify your functions a bit:
You have to return your values, otherwise your functions will return NULL by default. Also you can access a string like an array, so I used $company[0] to get the first letter of the company, which you then can concatenate with the size.
<?php
function bdads($size, $company) {
return $company[0] . $size;
}
function bdad($size, $company){
if($company == "both") {
$RandomList = [bdads($size, "gnr"), bdads($size, "nufa")];
return $RandomList[mt_rand(0, count($RandomList) - 1)];
} else {
return dads($size, $company);
}
}
echo bdad(300, "both");
?>
output:
n300 //Or g300