CODEWITHSUNDEEP
phpmysql
SkyLover
SkyLover

Reputation: 35

What does "= !" in the following PHP code mean?

When i run the sql script and substitute it with a numbers it return empty or null 

   $order_f = $dbs->query_field("SELECT order_id FROM orders WHERE order_center_id = !", $record['cust_id']);

What does the = ! stand for? Is this not equal?

Upvotes: 2

Views: 300

Answers (2)

Ja͢ck
Ja͢ck

Reputation: 173662

It's not an operator at all!

In your case it seems that the query_field() method that's provided by your database object (which I think is based on MDB2) provides some kind of prepared statement, where exclamation marks are used for place holders. I'm imagining that the following query is executed based on your code:

SELECT order_id FROM orders WHERE order_center_id = 123

Where 123 is the value of $record['cust_id'].

Old answer

In your case != (or <>) could be the same as =! (or = NOT(...)), because "not equal to" might be considered the same as "equal to inverse of", but only for boolean value logic. It will not work when you compare strings.

Also, there's a difference in operator precedence:

a = !b & c

This is evaluated as a = NOT(b) & c.

a != b & c

Whereas this is evaluated as a = NOT(b & c).

Upvotes: 7

spencer7593
spencer7593

Reputation: 108530

Q: What does the = ! stand for? Is this not equal?

No. A not equals comparator would be foo != bar or foo <> bar

I think you need to look at the query_field function to figure out what that's doing. It looks like the query is intended to do an equals comparison, and that exclamation point is a placeholder. (I'm not familiar with that query_field function; it doesn't look like a mysql_, mysqli_ or a PDO function, at least, that I've ever seen.)

What is $dbs? What kind of object is that? I bet that's where this method is defined.

I suspect someone has added a layer, on top of mysql interface, to pseudo-support paramaterized queries. Likely, that second argument to the function gets run through mysql_real_escape_string, before it's included in the SQL text, replacing the bang (!). That seems the most likely explanation.

Upvotes: 7

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