Why does directory listing wih array_push gives warning "the first argument is not an array" ?

[eaglehopes]

I read that array_push() can give warning when the first argument is not an array from php manual. However, my below code is for directory listing. Although there is no int variable in directory names(I checked all filenames-all string- but maybe implicit conversion is done??) randomly it gives warning. And it when I wrote the array  with var_dump() it writes some strange "int(1)", "int(4)" etc. as a result. Can someone explain where is my mistake?

My code for recursive directory listing with array_push() function ;

  function listAllFiles($dir) {
    $array = array_diff(scandir($dir), array('.', '..')); // remove "." and ".." folders
    foreach ($array as $f) {
      $sf = $dir.DIRECTORY_SEPARATOR.$f ;
      if(is_dir($sf)) {
		if(!is_array($array)){
          	echo "...no array...";
          	var_dump($array);  
			$array=[];
        } // end is_array check
        $array = array_push($array, listAllFiles($sf));
        echo "<br><b>".$sf." is a directory</b><br>";
      } else if(is_file($sf)) { echo "<br>".$sf." is a file"; } // end "if file/directory" check
    }  // end outer for loop
    return $array;
  }

Thanks.

[requinix]

What is the second argument to array_push supposed to be? What is the return value?

[eaglehopes]

3 minutes ago, requinix said:

What is the second argument to array_push supposed to be? What is the return value?

Thanks requinix. In manual page it says that : 

"array_push() treats array as a stack, and pushes the passed variables onto the end of array. The length of array increases by the number of variables pushed."

It should be "mixed" variable. In my code it should be an array(named $array) since it calls recursively the same function... So why the first argument gives an error then? Is it better to use array_merge() instead of array_push() then? I will try...

[requinix]

The second argument to array_push is the item you want to push. It is not an array of items you want to append. So that's a problem, though a bit separate from what you're looking at now.

How about the return value?

[eaglehopes]

2 minutes ago, requinix said:

How about the return value?

 Yes, you are right, it is integer ! Oh my god! My mistake is using array_push()... Thanks requinix! So, my final code using array_merge() was completely warning free now. 

 $array = array_merge($array, listAllFiles($sf));