Got it figured out. For reference for anyone else here is what I did.
PHP Code:
IP_ADDR_VAL=(echo "$ipadd | grep -Ec ^(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9])\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[1-9]|0)\.(25[0-5]|2[0-4][0-9]|[0-1]{1}[0-9]{2}|[1-9]{1}[0-9]{1}|[0-9])'")
if ! [ IP_ADDR_VAL == 0 ]; then
echo -e "Bad IP address: $ipadd\nTry again with correct IP Address.\nNo data has been entered into DNS."
exit 2
fi