How to echo with PHP this MySQL command

The following code gives me the following:

$getexpenses = "SELECT sum(expense_amount) FROM projects_expense WHERE project_id=$project_id";     
    $showexpenses = @mysqli_query ($dbc, $getexpenses); // Run the query.

    echo ' . $showexpenses . ';

Gives me a result of

' . $showexpenses . '

instead of 开发者_运维问答the actual sum...

I'm sure it's something simple I'm missing... thanks!

echo " . $showexpenses . " will work for you. You need double quotes, not single.

I added a call to mysqli_fetch_assoc($showexpenses)to make it fully functional. I also sanitized $project_id to avoid injections and used an alias to make the sum accessible through an associative array.

$getexpenses = "SELECT SUM(`expense_amount`) as `sum_amount` FROM `projects_expense` WHERE `project_id`= ".intval($project_id);     
$showexpenses = mysqli_query ($dbc, $getexpenses);
$sums = mysqli_fetch_assoc($showexpenses);
$sum = $sums['sum_amount'];

echo $sum;

We could also have used mysqli_fetch_row like this:

$getexpenses = "SELECT SUM(`expense_amount`) FROM `projects_expense` WHERE `project_id`= ".intval($project_id);     
$showexpenses = mysqli_query ($dbc, $getexpenses);
$sums = mysqli_fetch_row($showexpenses);
$sum = $sums[0];

echo $sum;

The alias is not needed anymore since we know the first column (0) is a match.

NB: you probably also need to GROUP BY project_id if you want to use SUM()

use

   echo $showexpenses;

or

echo "My query is: {$showexpenses}";

Further to Nik's response, PHP treats strings differently based on whether you use Single Quotes or Double Quotes around them.

Single-Quotes interpret text as literal text except for '\'' which would output a single quote mark and '\' which would output a slash mark. For this reason, using single quotes would output your variable name instead of the value.

Examples:

CODE             | OUTPUT
-----------------+------------------
echo '\t';       | \t
echo '\r';       | \r
echo '$foo';     | $foo

Double-Quotes interpret certain escape sequences for special characters and also interpret variables. For instance, "\n" ouputs a linefeed and "\r" outputs a carriage return. For this reason, echoing "$myvariable" outputs the value instead of the variable name.

Examples:

CODE             | OUTPUT
-----------------+------------------
echo "\t";       | {tab space}
echo "\r";       | {carriage return}
echo "$foo";     | bar

More reading: http://www.php.net/manual/en/language.types.string.php