- is_numeric: documentation ( source)
<?php
$a = '10';
$b= '50';
echo $a."\n";
echo $b."\n";
echo (($a * $b) . '')."\n";
$f = (($a * $b) . '');
echo gettype($f)."\n";
echo (!is_numeric(($a * $b) . '')) ? "yes right way \n":"not number...\n";
echo (($a * $b) != INF) ? "YES infinite.. \n":"NOt inf ... \n";
if(!is_numeric (($a * $b) . '') && (($a * $b) != INF))
{
echo "good\n";
}else{echo "WRONG...\n";}