Question

The PHP docs for join() and explode() say that the $glue and $delimiter must be strings. I tried this and it doesn’t throw any errors:

$glue = -8.5;
$delimiter = 0;
echo join( $glue, explode($delimiter, '1_0_1') ); // '1_-8.5_1'

So if I’m checking a $var that could be used as $glue or $delimiter, then is it safe to use is_string($var) || is_numeric($var)
as a condition OR are there times where that could be true but there’d be an error from the join() or explode()?

Answer 1

You can just do type casting like this:

// note join() is just an alias for implode. 
// i like the symmetry of using implode/explode
echo implode((string) $glue, explode((string) $delimiter, '1_0_1'));

At any rate, it appears they were being converted anyway.

Still, it would be good to use is_string() and is_numeric() to avoid a catchable fatal error if, say, an object was passed.

if ((is_string($glue) || is_numeric($glue))
    && (is_string($delimiter) || is_numeric($delimiter))
) {
    // objects didn't pass the test, safe to type-cast
    echo implode((string) $glue, explode((string) $delimiter, '1_0_1'));
}

---

Edit

Per ryanve’s suggestion, you could do this too:

if (is_scalar($glue) && !is_bool($glue)) { // ...