How to echo a PHP variable from MySQL results - php

Question

To automate my PHP to generate JSON, I saved the name of variable in database
(e.g. > $test_value_1).
In my php file I have the value of this variable (e.g. > $test_value_1 = "TEST VALUE 1")
After this I do a query to echo this variable, but, instead of returning the value of variable (TEST VALUE 1), always return just the text save in database ("$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.