How can PDO not return a row which pg_query() does?

问题

I had a table with a bigserial PK, one character varying FK and a bigint FK and a unique constraint on these FKs, a character varying NOT NULL and two nullable smallints.

All of this was running in a VM with Ubuntu 14.04.2 LTS, PHP 5.5.9 and PostgreSQL 9.3 and all other packages from the distribution.

I did

$pdo->query("SELECT * FROM table")->fetchAll(PDO::FETCH_ASSOC)

and

$r = pg_query($db, "SELECT * FROM table");
pg_fetch_all($r)

The latter returned all rows while the former returned all rows except for one.

I tried to select that very row as well, and while the pg_*() functions worked as expected, PDO did not return any row.

To make it even stranger, the discrepancy only emerged in PHP-FPM with lighttpd 1.4.33, but not when run with PHP CLI in a shell.

How can that be? Did anyone else encounter a similar situation? And how can I be sure that PDO will not fail me again?

I even tried rebooting the VM and restarted PostgreSQL, but the results did not change.

Sadly, I do not have a backup of this stuff because I had to get things working ASAP, so I deleted that mysterious row and replaced it with a new one, identical in all columns except for the PK.

The new row was returned properly by both.