how to get all href links from web url

<?php
  function get_all_links($url) {
     
    $content =file_get_contents($url);

    $textLen = strlen($content);
    if ($textLen > 10) {
     $hrefs = array();
     $dom = new DOMDocument();
     $dom->loadHTML($content);

     $tags = $dom->getElementsByTagName('a');
     foreach ($tags as $tag) {
        $href=$tag->getAttribute('href'); 
       $hrefs[] = $href ; 
     
    }
  }
   return array_flip(array_flip($hrefs));
      
}
get_all_links("put here url ") 
  ?>

    $content =file_get_contents($url);

$dom = new DOMDocument();
 $dom->loadHTML($content);
 $tags = $dom->getElementsByTagName('a');

   return array_flip(array_flip($hrefs)); // array_flip remove all duplicate urls