How to echo the value of a variable from the query result

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To automate my process of generating one JSON, i save the variable name in the database (Ex: $teste_value_1).

In my php file. i have the value of this variable, for example $teste_value_1 = "Isso é um teste";.

Then I make one query to echo this variable, however, instead of returning me the value of the previously predicted variable in PHP ("This is a test"), it always returns without interpreting the variable, only as text ("$teste_value_1").

Below my data structure to better understand the process:

Table: Attributes

id_attribute |  attribue_string | attribute_value
1            |  teste_string_1  | $teste_value_1
2            | teste_string_2   | $teste_value_2

Variables:

$teste_value_1 = "Isso é um teste";
$teste_value_2 = "Esse é outro teste";

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"] . ",";

Upshot: 

{id:teste_string_1,value_name:$teste_value_1},
{id:teste_string_2,value_name:$teste_value_2},

Expected result:

{id:teste_string_1,value_name:Isso é um teste},
{id:teste_string_2,value_name:Isso é outro teste},
php mysql json query variables

  • Perhaps it would be more feasible to save json directly to the database. Saving to the php variable name will not work. php interpolates the variable written to the file under some conditions. A string containing the variable will not be interpreted like this.

1 answer

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You can do this through a method called gambiarra. With this method you can call the function get_defined_vars() and it will return all variables declared. So you can search and replace the value $nome_da_variavel value returned by database.

Following example commented:

<?php

$teste_value_1 = "###########";
$teste_value_2 = "***********";

$text = '{id:"teste_string_1",value_name:"$teste_value_1"}, {id:"teste_string_2",value_name:"$teste_value_2"}';

/* Percorre todas as variáveis declaradas. */
foreach(get_defined_vars() as $variable => $value) {

    /* Verifica se o valor da variável é do tipo String */
    if (is_string($value)) {

        /* Realiza a busca e substituição */
        $text = str_replace(
                "\${$variable}",
                $value,
                $text
            );
    }
}

echo $text;

Obs.: This is not recommended, but in your case it will work. Ideally you could save the content in DB.

If you know the name of the variables and they do not change the name, just use the str_replace, for example:

$text = str_replace('$teste_value_1', $teste_value_1, $text);
$text = str_replace('$teste_value_2', $teste_value_2, $text);

echo $text;

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