I wanna pass a variable, but always get the error message

Invalid argument supplied for foreach()...

Here is my code:

function second($taxonomies)
    global $wpdb;
    $result = $wpdb->get_results( "SELECT * FROM tblTest WHERE manufacturer = $d", $taxonomies);
    foreach ($result as $pointer) {
    $id = $pointer->id;
    $car = $pointer->car;
    $price = $pointer->price;
    echo $id." ".$car." ".$price."<br />";

And how can I pass the result to another drop down? Thanks in advance!

2 Answers 2


As you can see in the Codex pages the get_results doesn't provide the functionality to add a value parameter in the method:

$wpdb->get_results('query', output_type);

output_type has the following description:

One of four pre-defined constants. Defaults to OBJECT. See SELECT a Row and its examples for more information.

  • OBJECT - result will be output as a numerically indexed array of row objects.
  • OBJECT_K - result will be output as an associative array of row objects, using first column's values as keys (duplicates will be discarded).
  • ARRAY_A - result will be output as an numerically indexed array of associative arrays, using column names as keys.
  • ARRAY_N - result will be output as a numerically indexed array of numerically indexed arrays.

You could use the following:

$results = $wpdb->get_results(
    SELECT *
     FROM tblTast
     WHERE manufacturer = %d

if ( $results ) {
  foreach ( $results as $pointer ) {
    /* your code here */

We'll add the 'prepare' method to make sure we're not dealing with an illegal operation or any illegal characters

See the Codex for more information.

$result = $wpdb->get_results(
        "SELECT * FROM tblTest WHERE manufacturer = %d",

See the codex on wpdb::prepare()

  • Thanks, but it looks like my variable is empty, cause I don'T get a result.
    – user35227
    Jul 12, 2013 at 9:22
  • Here is my code to call the function. So why is my variable empty? <form action="<?php bloginfo('url'); ?>" method="get"> <?php $taxonomies = 'Mustang'; $select = second($taxonomies); echo $select; ?> <noscript><div><input type="submit" value="Go" /></div></noscript> </form> What I also will do, but don't know how: To read the taxonomy from my site and compare it with my database query, the results will be shown.
    – user35227
    Jul 12, 2013 at 9:27

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