Variable in Array Not Working

Question

I having an issue getting a variable to work for one of my arguments in a query. I am using a custom post type and category name as terms to determine which categories are displayed.

When I hardcode the values into the terms it works fine, but when I use a variable it doesn't seem to work.

This code works:

$args = array(
    'post_type' => 'sparknz',
    'tax_query' => array(
        array(
            'taxonomy'  => 'sparknz_gardens',
            'field'     => 'name',
            'terms'     => array ( 'The A Team', 'The B Team', 'The C Team' ),
        )
    )
);  

But this does not (notice variable in terms):

$my_term_names = "'The A Team','The B Team','The C Team'";

$args = array(
    'post_type' => 'sparknz',
    'tax_query' => array(
        array(
            'taxonomy'  => 'sparknz_gardens',
            'field'     => 'name',
            'terms'     => array( $my_term_names ),
        )
    )
);

I need the terms to be a variable. Any Ideas?

Just an update as to why I am using a string as a variable. I am using array_intersect to pick out similarities in two arrays:

$my_user_array  = array( "c" => $user_array );
$my_cat_array   = array( "d" => $category_array );
$myresult       = array_intersect( $my_user_array, $my_cat_array );
$my_term_names  = implode( ",", $myresult );

echo $$my_term_names;

Not sure if there is another way to do this?

Answer 1

PHP interprets those arrays differently. In the first example you're asking WP_Query to get posts
by 3 term slugs and in the second example you're assigning the array a value of 1 string. If we were to print the two arrays it would look like this:

Your Example 1:

'terms' => array(
    [0] => 'The A Team',
    [1] => 'The B Team',
    [2] => 'The C Team'
)

Your Example 2:

'terms' => array(
    [0] => '\'The A Team','The B Team','The C Team\''
)

PHP thinks that you're assigning it a single string, even if there's commas in the string itself it is an absolute string. What you'll need to do is make the variable itself an array.

$my_term_names = array(
    'The A Team',
    'The B Team',
    'The C Team'
)

'terms' => $my_term_names

Answer 2

The following code is represented as one continuous string:

$my_term_names = "'The A Team','The B Team','The C Team'";

You want these terms to be an array:

$my_term_names = array( 'The A Team', 'The B Team', 'The C Team' );

Now you need to remove the array() from your terms query.

$args = array(
    'post_type' => 'sparknz',
    'tax_query' => array(
        array(
            'taxonomy' => 'sparknz_gardens',    // taxonomy name
            'field'    => 'name',               // term_id, slug or name
            'terms'    => $my_term_names,       // Terms array (defined above)
        )
    )
);

Edit. 10/19/2016

I realize you want to find the similarities between multiple arrays using array_intersect(); however, you need to stop trying to bring everything back into string format once you have your similarities located. array_intersect(); takes multiple arrays, finds the similarities, and returns a new array, containing the similar values between the multiple arrays specified.

Example #1 array_intersect() example

$array1 = array( "a" => "green", "red", "blue" );
$array2 = array( "b" => "green", "yellow", "red" );
$result = array_intersect( $array1, $array2 );
print_r( $result );

The above example will output:

Array
(
    [a] => green
    [0] => red
)

If you plan on retrieving multiple terms from your tax_query, the terms argument of the tax_query needs to be in array format . Not string format.

Here's an updated example for your situation. I've used simple variable names to get the point across:

$terms_array_1 = array( 'The B Team', 'The D Team', 'The A Team' );
$terms_array_2 = array( 'The A Team', 'The B Team', 'The C Team' );

$similar_terms = array_intersect( $terms_array_1, $terms_array_2 );

print_r( $similar_terms );

$args = array(
    'post_type' => 'sparknz',
    'tax_query' => array(
        array(
            'taxonomy' => 'sparknz_gardens',    // taxonomy name
            'field'    => 'name',               // term_id, slug or name
            'terms'    => $similar_terms,       // Term Names array (similarities between array1 and array2)
        )
    )
);