How to use View PHP in Exposed filters

Hi,

I would like to have one sample code like how to use views php when we are trying to do with exposed filter option, for eg i have tried views php to alter the value of Avalability status of one field from 0 and 1 to Yes or No, code below for reference,

if($row->Availability_of_Pharmacy_or_ChemistShop_within_Hospital == 1){
echo "Yes";
}else{
echo "No";
}

above code worked by simple logic, but how to code for Exposed filters with same functionality, like user has to have option to select value Yes or No by drop down, according to the value views should filter the same.

Thank you in advance.