Why doesn't separating the dollar sign work

[jasonkirk]

Setup a array that held all the query info for a database with the plan to put the second of code that updates the database into a function.  But hasn't been working.  In the end I widdled it down to the question, why don't these two bits of code work the same?

 

Array:

 

$database_info = array("db_table_name" => tbl_detentions, "db_field_names" => array("rel_student_uid", "detention_date"));

 

Database code:

 

$query = "INSERT INTO ". $database_info['db_table_name'];

$query .= " (" . $database_info['db_field_names'][0] . ", " . $database_info['db_field_names'][1] . ") VALUES ";

$query .= "($" . "rel_student_uid, '$detention_date')";

$result = mysql_query($query);

 

 

 

$query = "INSERT INTO ". $database_info['db_table_name'];

$query .= " (" . $database_info['db_field_names'][0] . ", " . $database_info['db_field_names'][1] . ") VALUES ";

$query .= "($rel_student_uid, '$detention_date')";

$result = mysql_query($query);

[blacknight]

$ in php marks the calling of a var weather it be array or what not if the $ is used improperly it will error out

 

$query .= "($" . "rel_student_uid, '$detention_date')";

 

reads the $ as a var call with no var name

 

$query .= "($rel_student_uid, '$detention_date')";

reads the $rel_student_uid as a var for php to call

 

any $ inside " " will be treated as a php var to avoid this if you are thing $ as just a character use mysql escape or enclose it in ' ' 

this making any $ inside a ' ' reas as text unless code escaped with ' ' . $var . ' ' or for doubles " " . $var . " " i personally always code escape my var and use mysql escape

 

i hope this helps

[jasonkirk]

Thanks it helps a bit though still haven't quite grasped. Tried making the original array variable have the $ instead of after the fact and using the mysql escape but still get the variable name $rel_student_uid instead of the actual uid.

 

 INSERT INTO tbl_detentions (rel_student_uid, detention_date) VALUES ('$rel_student_uid', '2013-3-3')

 

 

 

 

 

$database_info = array("db_table_name" => tbl_detentions, "db_field_names" => array("rel_student_uid", "detention_date"), "form_fields" => array('$rel_student_uid', "$detention_date"));

 

 

// Add detention to database BEGIN

$testt = mysql_real_escape_string($database_info['form_fields'][0]);

 

 

$query = "INSERT INTO ". $database_info['db_table_name'];

$query .= " (" . $database_info['db_field_names'][0] . ", " . $database_info['db_field_names'][1] . ") VALUES ";

$query .= "('" . mysql_real_escape_string($testt) . "', '$detention_date')";

$message .= $query;

$result = mysql_query($query);

if($result) {

$message .= "<center>Student given detention.</center>";

 

} else {

$message .= "Problem adding detention to student record.";

$message .= "<br>" . $query;

 

}

$detention_count++;

}

// Add detention to database END

 

[trq]

Variables are not interpolated within single quotes.

[jasonkirk]

Yea, I'm starting to see that treating ' and " the same has finally caught up and bit me.  I tended to do it to avoid escape characters so I could have quotes inside quotes without the confusion of \ all over the place.  Still haven't figured out the right combination yet.  I can break things worse but can't seem to go in the other direction.

[cyberRobot]

In some cases, you may want to consider removing the quotes altogether.

 

 

$database_info = array("db_table_name" => tbl_detentions, "db_field_names" => array("rel_student_uid", "detention_date"), "form_fields" => array($rel_student_uid, $detention_date));