How to properly use variable in a query? postgresql - php

Question

$result = pg_query(Postgres::getInstance(), "SELECT
date_start,
date_end,
cnt_hands,
cnt_hands_won,
amt_won,
id_session,
id_player,
amt_won
FROM
cash_table_session_summary
WHERE
date_start = '2016-04-27 07:20:47'");
This works perfectly.
echo $sessionStart;
$result = pg_query(Postgres::getInstance(), "SELECT
date_start,
date_end,
cnt_hands,
cnt_hands_won,
amt_won,
id_session,
id_player,
amt_won
FROM
cash_table_session_summary
WHERE
date_start = $sessionStart");
This throws this:
2016-04-27 07:20:47 Warning: pg_query(): Query failed: ERROR: syntax
error at or near "07" LINE 13: ... date_start = 2016-04-27 07:20:47 ^
in /home/haris/public_html/project/DAL_General.php on line 102
Is colon a problem? Do I need to escape it somehow? If so, how? I've google but found nothing about escaping colons.

Answer 1

Your date must be inside quotes. You need to change
FROM
cash_table_session_summary
WHERE
date_start = $sessionStart
To
FROM
cash_table_session_summary
WHERE
date_start = '$sessionStart'// add quotes here
For more understand about quotes check When to use single quotes, double quotes, and backticks in MySQL

Answer 2

I had the same issue when I was learning database work, but you need the query to be made in ""'s - Then when referencing a variable or data you need to put it in ''s, example:
$test_query = type_of_connection_query("SELECT * FROM users WHERE id = '1'");
That would not work like:
$text_query = type_of_connection_query("SELECT * FROM users WHERE id = 1");
And of course there are some times when you don't need quotes, like referencing LIMIT's
$text_query = type_of_connection_query("SELECT * FROM users WHERE id = '1' LIMIT 1");