<p>Is there any library function for this purpose, so I don't do it by hand and risk ending in TDWTF?</p>

<pre><code>echo ceil(31497230840470473074370324734723042.6);

// Expected result
31497230840470473074370324734723043

// Prints
&lt;garbage&gt;
</code></pre>

This will work for you:
```
```
$x = '31497230840470473074370324734723042.9';

bcscale(100);
var_dump(bcFloor($x));
var_dump(bcCeil($x));
var_dump(bcRound($x));

function bcFloor($x)
{
    $result = bcmul($x, '1', 0);
    if ((bccomp($result, '0', 0) == -1) && bccomp($x, $result, 1))
        $result = bcsub($result, 1, 0);

    return $result;
}

function bcCeil($x)
{
    $floor = bcFloor($x);
    return bcadd($floor, ceil(bcsub($x, $floor)), 0);
}

function bcRound($x)
{
    $floor = bcFloor($x);
    return bcadd($floor, round(bcsub($x, $floor)), 0);
}
```
```
Basically it finds the flooy by multiplying by one with zero precision.
Then it can do ceil / round by subtracting that from the total, calling the built in functions, then adding the result back on
Edit: fixed for -ve numbers