Replace usages of deprecated `$php_errormsg`

The PHP native `$php_errormsg` variable has been deprecated as of PHP
7.2. The recommended replacement is `error_get_last()`.

A number of the driver classes used  `$php_errormsg` to track if a DB
action caused an error.

As the `error_get_last()` function returns an array and comparing the
message therefore is slightly more involved, two new methods have been
introduced into the abstract parent class `ADOConnection` to handle the
message comparison.

The `resetLastError()` method retrieves the initial (old) error message
and resets it to enable checking whether a new error has occurred, even
when the new error is the same as the previous one.

The new `getChangedErrorMsg()` method compares the old error message
with the current one to determine whether a new message has occurred,
and if so, returns the message.

Refs:
* http://php.net/manual/en/migration72.deprecated.php#migration72.deprecated.track_errors-and-php_errormsg
* http://php.net/manual/en/reserved.variables.phperrormsg.php
* http://php.net/manual/en/function.error-get-last.php

Additional notes:
* In the `ADODB_ads::UpdateBlob()` method, the original (old) message
was not being retrieved which could result in an unrelated error being
recorded. This has been fixed.
* In the `ADODB_db2::_connect()` and `ADODB_db2::_pconnect()` methods,
the `$php_errormsg` was being reset, but subsequently not checked for
changes, so as the variable in effect was not being used, I've removed
the related code.
* In the `ADODB_sybase::ErrorMsg()` method, the `$php_errormsg` was
being checked, but no functions which could potential cause errors are
being called. As `$php_errormsg` is only available in the scope an
error occurred in, this meant that `$php_errormsg` would always be
empty, so I've removed the related code.

Fixes #409

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/adodb-odbtp.inc.php b/drivers/adodb-odbtp.inc.php
index 0420d02c..9a834707 100644
--- a/drivers/adodb-odbtp.inc.php
+++ b/drivers/adodb-odbtp.inc.php
@@ -609,7 +609,7 @@ class ADODB_odbtp extends ADOConnection{
 
 	function _query($sql,$inputarr=false)
 	{
-		error_clear_last();
+		$last_php_error = $this->resetLastError();
 		$this->_errorMsg = false;
 		$this->_errorCode = false;
 
@@ -619,8 +619,7 @@ class ADODB_odbtp extends ADOConnection{
 			} else {
 				$stmtid = @odbtp_prepare($sql,$this->_connectionID);
 				if ($stmtid == false) {
-					$err = error_get_last();
-					$this->_errorMsg = $err ? $err['message'] : '';
+					$this->_errorMsg = $this->getChangedErrorMsg($last_php_error);
 					return false;
 				}
 			}