Sort all words and write into a file

A PHP example to sort all words of a text in alphabetical order and write the words into a file.

<?php
function sort_all_words_and_write_into_file($text,$file){
preg_match_all("/[a-z0-9_\-]+/i",$text,$matches,PREG_PATTERN_ORDER);

$matches = array_unique($matches[0]);

natcasesort($matches);

$file_content = "";

while(current($matches)){
$file_content .= current($matches);

if(next($matches)){
$file_content .= "\r\n";
}
}

if(file_exists($file)){
if(is_writable($file)){
if(file_put_contents($file,$file_content)){
return true;
}
}
}else{
if(file_put_contents($file,$file_content)){
return true;
}
}

return false;
}

$text = "A PHP example to sort all words of a text in alphabetical order and write the words into a file.";

sort_all_words_and_write_into_file($text,"file.txt");
?>

The function returns false if the words haven't been written into the file.