Php check for single bit

Question

i've a Modbus response that is a 16bit byte. Every bit or couple of bit mean a specific state. (D15-14: Input volt status, D13: Charging mosfet is short, and so on).

I would like a easy way to print a string every time a single bit is different from previous.

For example: if the digit "14" changes, print "New volt status: Normal" if in the same time changes the D13 too, print "Charging mosfet is short".

I ended up with a not-elegant solution: a xor between the two values in order to check in which bit there is a change and then a for cycle through the XOR bits and than when the bit is on check the index of the bit and than many if (if $bit is 0 than "Mosfet is ok" else "Mosfet is in short"...

There is a quickest way? Thanx

you could print your number in binay into a string with something like $one_char_per_bit = sprintf("%016b", $Modbus_word), and then access each bit as a 0 or 1 character. — kuroi neko
– kuroi neko, Commented Feb 21, 2016 at 18:54

DianNianMao · Accepted Answer · 2016-02-21 19:30:31Z

1

as RiggiFolly directed.. you use the Binary operators:

<?php
    $value = 5;
    for($iShift = 0; $iShift < 8; $iShift++) {
        if($value & (1 << $iShift)) {
            echo "Bit " . ($iShift+1) . "  IS set\n";
        } else {
            echo "Bit " . ($iShift+1) . " NOT set\n";
        }
    }
?>

Hope that helps.. DNM

answered Feb 21, 2016 at 19:30

DianNianMao

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