How to recognize data type on PHP?

Question

i have some problem like this,

 i have string,

$str = "D33 D 123";

 after that, i explode it,

$str1 = explode(" ", $str);

 i make it into three variable,

$zero = $str1[0];
$one = $str1[1];
$two = $str1[2];

 how to recognize each variable as it's data type, for example the variable $three is recognized as int??

thanks