gistfile1.php

<?php

$resistor = array(
    1.0,
    1.1,
    1.2,
    1.3,
    1.5,
    1.6,
    1.8,
    2.0,
    2.2,
    2.4,
    2.7,
    3.0,
    3.3,
    3.6,
    3.9,
    4.3,
    4.7,
    5.1,
    5.6,
    6.2,
    6.8,
    7.5,
    8.2,
    9.1,
);

function Vovp($r1, $r2) {
    $Vfb = 1.235;
    return (($r1+$r2)/$r2)*$Vfb;
}

foreach($resistor as $r2) {
    foreach($resistor as $r1) {
        $v = Vovp($r1, $r2);
        if(round($v) == 5) {
            echo "Vovp=$v; R1=".($r1).", R2=$r2\r\n";
        }
    }
}