To extract the contents of a PKCS12 file you can use file_get_contents as well:
<?
$certs = array();
$pkcs12 = file_get_contents( "pkcs12file.pem" );
// No password
openssl_pkcs12_read( $pkcs12, $certs, "" );
print_r( $certs );
?>
Output is:
Array
(
[cert] => --- BEGIN CERTIFICATE ---
//snipsnip//
--- END CERTIFICATE ---
[pkey] => --- BEGIN RSA PRIVATE KEY ---
//snipsnip//
[extracerts] = Array
(
)
)