Description:
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password hashed using crypt() with a different algorithm than the one chosen for password_needs_rehash() are not considered as needing to be rehashed.

This behaviour is different than the one of PHP 7.1 to PHP 7.3.

Test script:
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<?php

var_dump(password_needs_rehash(crypt('Example', '$1$'), PASSWORD_DEFAULT)); // CRYPT_MD5
var_dump(password_needs_rehash(crypt('Example', '$6$rounds=5000$aa$'), PASSWORD_DEFAULT));  // CRYPT_SHA512 with 5000 rounds

Expected result:
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bool(true)
bool(true)

Actual result:
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bool(false)
bool(false)