I was searching for a solution to make key files available in my Heroku app without adding it to the repository. Using a streamwrapper doesn't work, because ssh2 only accepts strings to files without a schema part. But still want to share this very useless class with you. "echo file_get_contents( 'env://ENV_VAR' );" does exactly the same as "get…

EnvStream.php

<?php

class EnvStream
{
  private $var, $position = 0;

  function stream_open($path, $mode, $options, &$opened_path)
  {
      $this->var = parse_url( $path, PHP_URL_HOST );
      return true;
  }
  
  function stream_read($count)
  {
    if( $this->position > 0 )
      return null;
    
    $ret = getenv( $this->var );
    $this->position += strlen( $ret );
        return $ret;
  }
  
  function stream_seek($offset, $whence)
  {
    switch ($whence) {
        case SEEK_SET:
          if ($offset < strlen( getenv( $this->var )) && $offset >= 0) {
            $this->position = $offset;
            return true;
          } else {
            return false;
          }
        break;

        case SEEK_CUR:
          if ($offset >= 0) {
            $this->position += $offset;
            return true;
          } else {
            return false;
          }
        break;

        case SEEK_END:
          if (strlen(getenv( $this->var )) + $offset >= 0) {
            $this->position = strlen(getenv( $this->var )) + $offset;
            return true;
          } else {
            return false;
          }
        break;

        default:
          return false;
        }
  }

  function stream_eof()
  {
    return $this->position >= strlen( getenv( $this->var ));
  }
  
  function stream_tell()
  {
    return $this->position;
  }
  
  function stream_stat()
  {
    return [ 
      'size' => strlen( getenv( $this->var ))
    ];
  }
}

example.php

<?php

include( 'EnvStream.php' );

stream_wrapper_register("env", "EnvStream")
	or die("Failed to register protocol");
			
echo file_get_contents( "env://ENV_VAR" ); // Prints content of ENV_VAR

$connection = ssh2_connect( 'your.server', 22 ); 

// Prints the error "Unable to open public key file"
ssh2_auth_pubkey_file( $connection,
  'root',
  'env://PUBLIC_KEY',
  'env://PRIVATE_KEY'
);