You have to make the variable name with the curly brackets.. I don't think you can have a number as a variable name, so you may have to prefix it with a letter or some other text.
Hope it helps.
Code
$b1[0]='ooh';
$b1[1]='la';
$b1[2]='lah';
echo "1. ".${'b'.'1'}[0]."<br>";
echo "2. ".${'b'.'1'}[1]."<br>";
echo "3. ".${'b'.'1'}[2]."<br>";
foreach (${'b'.'1'} as $bip) {
echo $bip."<br>";
}
Screen Output
1. ooh
2. la
3. lah
ooh
la
lah