PHP openssl_spki_verify() Function

<?php
 
error_reporting(E_ERROR  | E_PARSE);

/* Array of private key sizes to test */
$ksize = array('1024'=>1024,
               '2048'=>2048,
               '4096'=>4096);
 
/* Array of available hashings to test */
$algo = array(
    'sha512'=>OPENSSL_ALGO_SHA512,
    'rmd160'=>OPENSSL_ALGO_RMD160
);
 
/* Loop over key sizes for test */
foreach($ksize as $k => $v) {
 
    /* generate new private key of 
    specified size to use for tests */
    $pkey = openssl_pkey_new(array
        ('digest_alg' => 'sha512',
        'private_key_type' => OPENSSL_KEYTYPE_RSA,
        'private_key_bits' => $v)
    );
    
    openssl_pkey_export($pkey, $pass);
 
    /* Loop to create and verify results */
    foreach($algo as $key => $value) {
        $spkac = openssl_spki_new(
                $pkey, _uuid(), $value);
                
        echo "Positive verification:: Algo: "
                . $key . ", value:";
        
        var_dump(openssl_spki_verify(
            preg_replace('/SPKAC=/', '', $spkac)));
            
        echo "Negative verification:: Algo: "
                . $key . ", value:";
        var_dump(openssl_spki_verify(
                $spkac . 'Make it fail'));
        echo "\n";
    }
    openssl_free_key($pkey);
}
 
/* Generate a random challenge */
function _uuid() {
    return sprintf(
        '%04x%04x-%04x-%04x-%04x-%04x%04x%04x', 
        mt_rand(0, 0xffff), mt_rand(0, 0xffff), 
        mt_rand(0, 0xffff), mt_rand(0, 0x0fff) | 0x4000,
        mt_rand(0, 0x3fff) | 0x8000, mt_rand(0, 0xffff),
        mt_rand(0, 0xffff), mt_rand(0, 0xffff)
    );
}
?>