Question

Is there any way in PHP to open a file based on a variable for the filename? Basically what I want to is this:

$file = file('data.txt');
$needle = array("one", "two", "three");
$haystack = array("one", "three");

foreach($needle as $value){
  $pos = strpos($haystack, $value);

if($pos !== false){
  $filename = "$value.txt";
  file_put_contents($filename, $file);
}

The values of $needle are the names of .txt files. It works up until file_put_contents. $filename is not valid and I have searched all over for a solution to this and tried everything I can think of. I want to load the array value, say “one” with the .txt extension as a filename, depending on if the value was found in the haystack. Is there any way to do this without doing an if statement for each filename? I would rather handle it with a loop if possible.

Edited to swap the parameters.

Edit, new code:

$data = file_get_contents('data.txt');
$needle = array("one", "two", "three");
$haystack = array("one", "three");
$files = array_intersect($needle, $haystack);
foreach ($files as $value) {
  $newfilename = "$value.txt";
  var_dump($newfilename);
  file_put_contents($newfilename, $data);
}

Answer 1

You mixed up the parameters of file_put_contents():

int file_put_contents ( string $filename , mixed $data [, int $flags = 0 [, resource $context ]] )

So you need to swap them:

file_put_contents($filename, $file);

Second thing is, that you’re doing a strpos() on an array, but that function is (as its name says) for strings – what you want is in_array():

foreach ($needle as $value) {
    if (in_array($value, $haystack) {
        $filename = "$value.txt";
        file_put_contents($filename, $file);
    }
} 

You can even enhance this a bit more by using array_intersect() – that gives you an array of all the value from $needle that are also in $haystack. I think that’s what you were asking for to avoid the if statement:

$files = array_intersect($needle, $haystack);
foreach ($files as $value) {
    $filename = "$value.txt";
    file_put_contents($filename, $file);
}