postgres stored procedure json error - php

Question

So I'm making a application where I want a json string to display(for now). I call a stored procedure with php(which works) and that stored procedure returns a row.
The problem is that the record/row that is returned has to be a json string. For that I use php:
$verbinding = pg_connect("host=**** port=**** dbname=*** user=******* password=****");
$query = 'SELECT to_json(function_name(parameter))';
$contests = pg_query($query);
if(json_decode($contests)) {
echo 'succeeded';
} else {
echo 'failed';
}
Now my code always returns failed and I don't know why or how can I fix this. Thank you in advance for your help!

Answer 1

This:
$contests = pg_query($query);
json_decode($contests)
is nonsensical. If you replace json_decode with a print statement you will see why.
Per the manual the return value of pg_query is:
A query result resource on success or FALSE on failure.
and if you look at the examples, you will see some basic usage, where you will see that you need to use pg_fetch_row or similar to access the results.
This makes sense given that a query result can have multiple rows and multiple values per row.
The "See also" section of the documentation link above points you at the functions you need.
In this case I suggest using pg_fetch_result (see the sidebar).
While you're at it some basic error handling would be wise.
I also strongly suspect you're failing to use bind parameters, exposing yourself to SQL injection. Use pg_query_params.
Here's a starting point for you. It's untested, and I don't really use PHP, but it should give you an idea where you're going wrong:
$query = 'SELECT to_json(function_name($1))';
$contests = pg_query_params($query, array($somevariable))
or die(pg_last_error());
$json = pg_fetch_result($contests, 0, 0);
if(json_decode($json)) {
# ....
}
Now, seriously, go read the manual.