Try looking in the content_node_field table, under the global settings value:
mysql> desc content_node_field;
+-----------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+--------------+------+-----+---------+-------+
| field_name | varchar(32) | NO | PRI | | |
| type | varchar(127) | NO | | | |
| global_settings | mediumtext | NO | | NULL | |
| required | tinyint(4) | NO | | 0 | |
| multiple | tinyint(4) | NO | | 0 | |
| db_storage | tinyint(4) | NO | | 1 | |
| module | varchar(127) | NO | | | |
| db_columns | mediumtext | NO | | NULL | |
| active | tinyint(4) | NO | | 0 | |
| locked | tinyint(4) | NO | | 0 | |
+-----------------+--------------+------+-----+---------+-------+
I just did a test, defining an arbitrary PHP string (print "Hello Stack Exchange";) under allowed values for a field (field_test2) and found the following:
mysql> select global_settings from content_node_field where field_name = "field_test2";
+----------------------------------------------------------------------------------------------------------------------------------------------------+
| global_settings |
+----------------------------------------------------------------------------------------------------------------------------------------------------+
| a:4:{s:15:"text_processing";s:1:"0";s:10:"max_length";s:0:"";s:14:"allowed_values";s:0:"";s:18:"allowed_values_php";s:31:"print "Hello Stack Exchange";";} |
+----------------------------------------------------------------------------------------------------------------------------------------------------+
The string you are looking for is at the end (s:31:"print "Hello Stack Exchange";";) and it's serialized with the character count at the front. If you want to zero this out, it would look like:
a:4:{s:15:"text_processing";s:1:"0";s:10:"max_length";s:0:"";s:14:"allowed_values";s:0:"";s:18:"allowed_values_php";s:0:"";}