如何从MySQL结果中回显PHP变量

Question

To automate my PHP to generate JSON, I saved the name of variable in database (eg > $test_value_1 ).

In my php file I have the value of this variable (eg > $test_value_1 = "TEST VALUE 1" )

After this I do a query to echo this variable, but, instead of returning the value of variable (TEST VALUE 1), always return just the text save in database ("$teste_value_1")

To understand better, look my database, variable, query, response and what I need:

TABLE: attributes

   id_attribute |  attribue_string | attribute_value
    1            |  test_string_1  | $test_value_1
    2            |  test_string_2  | $test_value_2

VARIABLES:

$test_value_1 = "Test Value 1"; 
$test_value_2 = "Teste Value 2";

QUERY:

$query_array = mysqli_query($connect,"
    SELECT GROUP_CONCAT(CONCAT('{id:', a.attribute_string, ',value_name:', a.attribute_value, '}') SEPARATOR ', ') AS concat
    FROM rel_categories_attributes AS rca
    INNER JOIN categories AS c ON c.id_category = rca.categories_id_category
    INNER JOIN attributes AS a ON a.id_attribute = rca.attributes_id_attribute
    WHERE id_category = '{$id_category}'
    ");
WHILE ($reg_cat = mysqli_fetch_array($query_array)){

    echo $teste_query = $reg_cat["concat"] . ",";

RESPONSE: {id:test_string_1,value_name:$test_value_1}, {id:teste_string_2,value_name:$test_value_2} , (WRONG)

WHAT I NEED: {id:test_string_1,value_name:TEST VALUE 1}, {id:teste_string_2,value_name:TESTE VALUE 2} ,

Answer 1

While this seems like a horrible design, you can do it using variable variables . But you'll need to do the output formatting in PHP, not in MySQL.

$query_array = mysqli_query($connect,"
    SELECT a.attribute_string, a.attribute_value
    FROM rel_categories_attributes AS rca
    INNER JOIN categories AS c ON c.id_category = rca.categories_id_category
    INNER JOIN attributes AS a ON a.id_attribute = rca.attributes_id_attribute
    WHERE id_category = '{$id_category}'
");

$result = array();
while ($row = mysqli_fetch_assoc($query_array) {
    $result[] = array('id' => $row['attribute_string'], 'value_name' => ${$row['attribute_value']});
}
echo json_encode($result);

However, variable variables can almost always be improved by using an associative array. Instead of having variables like $test_value_1 and $test_value_2 , create an array whose keys are "test_value_1" and "test_value_2" , and then use $array[$row['attribute_value']] .

But even better would be to put all the details in the database itself, rather than hard-coding them in the scripts. You can then join with that table to translate the attribute value to the appropriate string.