date syntax is not valid, PostgreSQL - postgresql

Question

I would like to query a column name's inputdate, type : date. When I query:
where (inputdate>='$VEStart' AND inputdate<='$VEEnd')
I got:
error : warning pg_query() query failed error invalid input syntax for date where (inputdate>='' AND inputdate<='').
But when I try to replace it:
where (inputdate>='2015-12-01' AND inputdate<='2015-12-31')
It works. I thought it was a problem with variables. so I tried to echo both variables, but they display the right values. Anything wrong here?

Answer 1

Just to give you an example beyond the comment, use something like this and ensure that you add improvements to the below code before putting it into production use; also test it well.
<?php
$VEStart = '2015-01-01';
$VEEnd = '2015-2-28';
// validate the dates
if (!isDateValid($VEStart)) {
print "Invalid start date\n";
return;
}
if (!isDateValid($VEEnd)) {
print "Invalid end date\n";
return;
}
// format the dates
$VEStart = formattedDate($VEStart);
$VEEnd = formattedDate($VEEnd);
echo sprintf ("all good - %s and %s\n", $VEStart, $VEEnd);
// see http://php.net/manual/en/function.pg-query-params.php
$sql = 'select ... where inputdate between $1 and $2';
$connection = pg_connect('...');
$result = pg_query_params($connection, $sql, array($VEStart, $VEEnd));
...more code...
// ----
// add good phpdoc
// see how others add doc - http://stackoverflow.com/questions/1904214/what-is-the-proper-php-function-documentation-format
function formattedDate($date) {
list($year, $month, $day) = explode('-', $date);
return date('Y-m-d', mktime(0, 0, 0, $month, $day, $year));
}
// add good phpdoc
function isDateValid($date) {
list($year, $month, $day) = explode('-', $date);
return checkdate($month, $day, $year);
}
?>