php pattern : test if properties exists and set defaults

php_function_arguement_defaults.php

/**
 * Function does something... 
 * @param obj $obj object with required and optional properties.
 */
function something($obj) {
    // bail if required properties aren't set
    if( !isset($obj->req_prop_1) || !isset($obj->req_prop_1) ) { return ''; }

    $opt_prop_1 = $obj->opt_prop_1;
    $opt_prop_2 = $obj->opt_prop_2;

    // set defaults
    if( !isset($opt_prop_1) ) { 
        $opt_prop_1 = 'n/a'; 
    }
    if( !isset($opt_prop_2) ) { 
        $opt_prop_2 = 0; 
    }

}

Can also store the required properties in their own variables too, and not use $obj->req_prop_1 everywhere.