How to do a meta query in WordPress:
$meta_query = array(
'relation' => 'OR',
array(
'relation' => 'AND',
array(
'key' => 'first_name',
'value' => $first_name
),
array(
'key' => 'last_name',
'value' => $last_name
),
array(
'relation' => 'AND',
array(
'key' => 'school',
'value' => $school
),
array(
'key' => 'department',
'value' => $department
),
),
)
);
$args = array (
'post_type' => 'staff',
'numberposts' => -1,
'orderby' => 'title',
'order' => 'ASC',
'meta_query' => $meta_query
);