Description:
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The documentation states
"Using the PASSWORD_BCRYPT as the algorithm, will result in the password parameter being truncated to a maximum length of 72 characters."
This is not true. The password is being truncated to a maximum length of 72 bytes. Since passwords should contain special characters, a lot of which are multi-byte, this should be clarified.
This is incorrect both on the documentation for password_hash() as well as the documentation for crypt().

Test script:
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$pw = str_pad("", 71, 'a');
$salt = ['salt' => 'N9qo8uLOickgx2ZMRZoMye'];
echo password_hash($pw . 'a', PASSWORD_DEFAULT, $salt ) . PHP_EOL;
echo password_hash($pw . 'ä', PASSWORD_DEFAULT, $salt ) . PHP_EOL;
echo password_hash($pw . 'ö', PASSWORD_DEFAULT, $salt ) . PHP_EOL;

Expected result:
----------------
Three differnt hashes

Actual result:
--------------
$2y$10$N9qo8uLOickgx2ZMRZoMye5mlC/WoAmNnGP3YkHGchsBkco85S4ZC
$2y$10$N9qo8uLOickgx2ZMRZoMyeWZPaNHNhngTN.zngPxYMmerH0ZknF7.
$2y$10$N9qo8uLOickgx2ZMRZoMyeWZPaNHNhngTN.zngPxYMmerH0ZknF7.