Description:
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looks like oci_bind_by_name has some memory allocation issue

when clave == '';
running oci_bind_by_name($stid, ":password", strtoupper($clave))
produces 'Only variables should be passed by reference' which is expected, but then all empty strings are string(6) "\x00\x00\x00\x00\x00\x00" instead of string(0) ""
substr("", 0, 0) still produces string(0) "" though


Test script:
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$clave = '';
oci_bind_by_name($stid, ":password", strtoupper($clave))
$test = ''; var_dump($test);
will produce string(6) "\x00\x00\x00\x00\x00\x00";

Expected result:
----------------
I expect 
$test = ''; var_dump($test);
to produce string(0) ""

Actual result:
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after reaching clave=""; oci_bind_by_name($stid, ":password", strtoupper($clave))

$test = ''; var_dump($test);
produces string(6) "\x00\x00\x00\x00\x00\x00"