manual mysql_real_escape_string()

Escapes special characters in a string for use in an SQL statement

So you can't escape entire query, just data because it will escape all unsafe characters like quotes (valid parts of query).

If you try something like that (to escape entire query)

echo mysql_real_escape_string("INSERT INTO some_table VALUES('xyz', 'abc', '123');");

Output is

INSERT INTO some_table VALUES(\'xyz\', \'abc\', \'123\');

and that is not valid query any more.

manual mysql_real_escape_string()

Escapes special characters in a string for use in an SQL statement

So you can't escape entire query, just data... because it will escape all unsafe characters like quotes (valid parts of query).

If you try something like that (to escape entire query)

echo mysql_real_escape_string("INSERT INTO some_table VALUES ('xyz', 'abc', '123');");

Output is

INSERT INTO some_table VALUES ('xyz', 'abc', '123');

and that is not valid query any more.