Fix character escaping to support escaped backslashes

Author: JanJakes

src/Import.php

@@ -102,8 +102,13 @@ public function parse_statements( $sql_file_path ) {
 			for ( $i = 0; $i < $strlen; $i++ ) {
 				$ch = $line[ $i ];
 
-				// Handle escaped characters
-				if ( $i > 0 && '\\' === $line[ $i - 1 ] ) {
+				// Count preceding backslashes.
+				for ( $slashes = 0; '\\' === ( $line[ $slashes - $i - 1 ] ?? null ); $slashes += 1 );
+
+				// Handle escaped characters.
+				// A characters is escaped only when the number of preceding backslashes
+				// is odd - "\" is an escape sequence, "\\" is an escaped backslash.
+				if ( 1 === $slashes % 2 ) {
 					$buffer .= $ch;
 					continue;
 				}