if problems

[Anon]

I am having a problem with an if-elseif statement. Each of the statements that just have one item in the if/esleif statement work. All of the statements that have two or three items/variables aren't working. What am I doing wrong?

if ($Make=='')
$sql = "SELECT * from new_cars where model = '$Model' and price
< '$Price' + 0";

else if ($Model=='')
$sql = "SELECT * from new_cars where make = '$Make' and price
< '$Price' + 0";

else if ($Price=='') {
$sql = "SELECT * from new_cars where make = '$Make' and model =
'$Model'";
}

else if (($Make=='') && ($Model==''))
$sql = "SELECT * from new_cars where price < '$Price' + 0";

else if (($Make=='') && ($Price==''))
$sql = "SELECT * from new_cars where model = '$Model'";

else if (($Price=='') && ($Model==''))
$sql = "SELECT * from new_cars where make = '$Make'";

else if (($Make!='') && ($Model!='') && ($Price!=''))
$sql = "SELECT * from new_cars where make = '$Make' and
model = '$Model' and price < '$Price' + 0";

else if (($Make=='') && ($Model=='') && ($Price==''))
$sql = "SELECT * from new_cars";

else
print "There was an error";

$result = mysql_db_query($dbname,$sql);

Jason Martin

[Anon]

Since I don't have your tables here to try this on, could you explain what is happening in these cases?

Also, you can really simplify all this by taking the opposite approach. Your code currently creates the query string based on which arguments are absent. Deciding based on which are present is easier; in fact you can create a function to do the hard part:

function set_condition( $result, $column, $value, $operator, $sep )
{
if ($value != '') // if arg is blank, don't do anything at all to the query string
&nbsp;&nbsp;&nbsp;{
&nbsp;&nbsp;&nbsp;if ($result == '') // first condition being added to query
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$result = ' where ';
&nbsp;&nbsp;&nbsp;else
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$result .= ' and ';
&nbsp;&nbsp;&nbsp;$result .= "$column $operator $sep$value$sep";
&nbsp;&nbsp;&nbsp;}
return $result
}

$sql = 'SELECT * from new_cars ';
$where = set_condition( $where, 'model', $Model, '=', "'");
$where = set_condition( $where, 'make', $Make, '=', "'");
$where = set_condition( $where, 'price', $Price, '&lt;', '');

echo "query = $sql";

To clarify those final parameters (which are quite hard to read): the first two are a single-quote; the last one is an empty string. The beauty of this system is that if you need to add more tests, all you have to do is add another function call--nothing you've previously written needs to be modified.

[Anon]

Um... Maybe I'm missing something here, but your code is way off. I think it should look like:

if(CONDITION) {

} # End if
elseif {

} # End elseif
else {

} # End else

You forgot all the {}s, and you're "else if" should be "elseif" - Maybe you're using shorthand code that works with one line below the if/elseif, but when you do two lines, it can't use the shorthand... I dunno.

[Anon]

I have a table called new_cars with the columns model, make, & price.

I have a form that allows the user to select the model, make, and/or price (enter maximum amount). The form then calls on another script which I listed in the previous post. I am just trying to search the new_cars table based on the data they put in the form and display the results. It works when they enter just one item, but when they enter two or all three items, it comes back with no data. It doesn't error out, it just comes back with no data.

On your example, I commented out my code & pasted your code, but it gives me a parse error. I am a bit of a newbie, so I truly appreciate your help. Below is the code of the whole script.

<?
$dbuser = '**';
$dbhost = '';
$dbpass = '';
$dbname = '**';
$dbtble = 'new_cars';
$mysql_link = mysql_connect($dbhost,$dbuser,$dbpass);
$column = mysql_list_fields($dbname,$dbtble,$mysql_link);
/
if ($Make=='')
$sql = "SELECT from new_cars where model = '$Model' and price
< '$Price' + 0";

else if ($Model=='')
$sql = "SELECT * from new_cars where make = '$Make' and price
< '$Price' + 0";

else if ($Price=='') {
$sql = "SELECT * from new_cars where make = '$Make' and model =
'$Model'";
}

else if (($Make=='') & ($Model==''))
$sql = "SELECT * from new_cars where price < '$Price' + 0";

else if (($Make=='') & ($Price==''))
$sql = "SELECT * from new_cars where model = '$Model'";

else if (($Price=='') & ($Model==''))
$sql = "SELECT * from new_cars where make = '$Make'";

else if (($Make!=='') & ($Model!=='') & ($Price!==''))
$sql = "SELECT * from new_cars where make = '$Make' and
model = '$Model' and price < '$Price' + 0";

else if (($Make=='') & ($Model=='') & ($Price==''))
$sql = "SELECT * from new_cars";

else
print "There was an erro";

$result = mysql_db_query($dbname,$sql);
if ($result=='')
echo "No rows.";

*/
function set_condition( $result, $column, $value, $operator, $sep )
{
if ($value != '') // if arg is blank, don't do anything at all to the query string
{
if ($result == '') // first condition being added to query
$result = ' where ';
else
$result .= ' and ';
$result .= "$column $operator $sep$value$sep";
}
return $result
}

$sql = 'SELECT * from new_cars ';
$where = set_condition( $where, 'model', $Model, '=', "'");
$where = set_condition( $where, 'make', $Make, '=', "'");
$where = set_condition( $where, 'price', $Price, '<', '');

echo "query = $sql";

?>

<table bgcolor="black">
<tr><td>
<table><!---- Inside Table ---->
<?

while($value = mysql_fetch_array($result))
{
print "<tr BGCOLOR=YELLOW>";
//This loop goes through the colums and prints
//each value
for($i=0; $i< mysql_num_fields($column); $i++ )
{
print "<td> $value[$i] </td>";
}
print "</tr>";
}
mysql_free_result($result);
mysql_close();
?>
</table><!---- Inside Table ----->
</td></tr>
</table>

[Anon]

your example... gives me a parse error

Sorry, I wrote it off the top of my head, so that's not terribly surprising. I'm having trouble spotting anything wrong (never be the primary tester of your own code!); which line is it complaining about?

Also, I've got a question about price: isn't this a numeric field in the database?

[Anon]

Actually, his is not wrong. PHP is like C in this regard, rather than like Perl: braces are optional if the body is only a single statement. And while PHP does supply 'elseif' and he probably should be using it, 'else if' also works fine--says so right here in the manual:

<b>In PHP, you can also write 'else if' (in two words) and the behavior would be identical to the one of 'elseif' (in a single word). The syntactic meaning is slightly different (if you're familiar with C, this is the same behavior) but the bottom line is that both would result in exactly the same behavior. </b>

[Anon]

I've attached the complete file with your code implemented. It doesn't like the last } after the
return $result.

Yes, price is a numeric field, that's why I was adding 0 to the value in my if statements to convert it to a number.

<?
$dbuser = '**';
$dbhost = '';
$dbpass = '';
$dbname = '**';
$dbtble = 'new_cars';
$mysql_link = mysql_connect($dbhost,$dbuser,$dbpass);
$column = mysql_list_fields($dbname,$dbtble,$mysql_link);

/
if ($Make=='') {
$sql = "SELECT from new_cars where model = '$Model' and price
< '$Price' + 0";
}

elseif ($Model=='') {
$sql = "SELECT * from new_cars where make = '$Make' and price
< '$Price' + 0";
}

elseif ($Price=='') {
$sql = "SELECT * from new_cars where make = '$Make' and model =
'$Model'";
}

elseif (($Make=='') & ($Model=='')) {
$sql = "SELECT * from new_cars where price < '$Price' + 0";
}

elseif (($Make=='') & ($Price=='')) {
$sql = "SELECT * from new_cars where model = '$Model'";
}

elseif (($Price=='') & ($Model=='')) {
$sql = "SELECT * from new_cars where make = '$Make'";
}

elseif (($Make!=='') & ($Model!=='') & ($Price!=='')) {
$sql = "SELECT * from new_cars where make = '$Make' and
model = '$Model' and price < '$Price' + 0";
}

elseif (($Make=='') & ($Model=='') & ($Price=='')) {
$sql = "SELECT * from new_cars";
}
else {
print "a is smaller than b";
}

$result = mysql_db_query($dbname,$sql);
if ($result=='')
echo "No rows.";
*/

function set_condition( $result, $column, $value, $operator, $sep )
{
if ($value != '') // if arg is blank, don't do anything at all to the query string
{
if ($result == '') // first condition being added to query
$result = ' where ';
else
$result .= ' and ';
$result .= "$column $operator $sep$value$sep";
}
return $result
}

$sql = 'SELECT * from new_cars ';
$where = set_condition( $where, 'model', $Model, '=', "'");
$where = set_condition( $where, 'make', $Make, '=', "'");
$where = set_condition( $where, 'price', $Price, '<', '');

echo "query = $sql";

?>

<table bgcolor="black">
<tr><td>
<table><!---- Inside Table ---->
<?

while($value = mysql_fetch_array($result))
{
print "<tr BGCOLOR=YELLOW>";
//This loop goes through the colums and prints
//each value
for($i=0; $i< mysql_num_fields($column); $i++ )
{
print "<td> $value[$i] </td>";
}
print "</tr>";
}
mysql_free_result($result);
mysql_close();
?>
</table><!---- Inside Table ----->
</td></tr>
</table>

Thanks,

Jason Martin

[Anon]

Jason what it doesn't like is that you forgot a semicolon on the end of the return $result line

[Anon]

All of the expressions in my code work except the one's with more than one expression. Is && the correct thing to use to combine the if statements. It seems as if this should be very easy, but for some reason it won't work with the if/esleif statement with more than 1 condition.

I've posted the code below again.

Jason Martin

if ($Make!='') {
$sql = "SELECT * from new_cars where make = '$Make'";
}

elseif ($Model!='') {
$sql = "SELECT * from new_cars where model = '$Model'";
}

elseif ($Price!='') {
$sql = "SELECT * from new_cars where price < $Price";
}

elseif (($Make!='') && ($Model!='')) {
$sql = "SELECT * from new_cars where make = '$Make' and
model = '$Model'";
}

elseif (($Make!='') && ($Price!='')) {
$sql = "SELECT * from new_cars where make = '$Make' and price <
$Price";
}

elseif (($Price!='') && ($Model!='')) {
$sql = "SELECT * from new_cars where model = '$Model' and
price < $Price";
}

elseif (($Make!='') && ($Model!='') && ($Price!='')) {
$sql = "SELECT * from new_cars where make = '$Make' and
model = '$Model' and price < $Price";
}

else {
$sql = "SELECT * from new_cars";
}

[Anon]

If / else if constructs work like this:

As soon as any ONE statement is true, all the following else ifs are skipped.

So...

if ($a==0){
function_1();
}else if ($a==0&&$b==0){
function_2();
}
....

If $a=0, then the first if is true. All subsequent else if's are tossed in the trash, and the second choice will never get executed.

Now,

if ($a==0){
function_1();
}
if ($a==0&&$b==0){
function_2();
}

Will execute both functions 1 and 2.

while:

if ($a==0&&$b==0){
function_2();
}else if ($a==0){
function_1();
}

will execute function_2 if both a and b are zero, but will execute function_1 if a is zero and b is non-zero