If you're curious to use this method to determine if there is someway to evaluate if a given string is NOT a password_hash() value...
<?php
// Our password.. the kind of thing and idiot would have on his luggage:
$password_plaintext = "12345";
// Hash it up, fuzzball!
$password_hash = password_hash( $password_plaintext, PASSWORD_DEFAULT, [ 'cost' => 11 ] );
// What do we get?
print_r( password_get_info( $password_hash ) );
/* returns:
Array (
[algo] => 1
[algoName] => bcrypt // Your server's default.
[options] => Array ( [cost] => 11 )
)
*/
// What about if it's un-hashed?...
print_r( password_get_info( $password_plaintext ) );
/* returns:
Array (
[algo] => 0
[algoName] => unknown
[options] => Array ( )
)
*/
?>
... Looks like it's up to each of us to personally decide if it's safe to compare against the final returned array.