在PHP中正确使用“&&”，“||”和“！=”

Question

I'm not too sure about PHP but I normally took it was like math and the brackets are done before anything else.

I have this:

if( !strncmp($method_id,'OPTION', 6) && ( ($method_id != 'OPTION_5') || ($method_id != 'OPTION_12') ) )
    unset( $available_methods[ $method_id ] );

Where $method_id is equal to OPTION_ 1 through to 12.

Effectively if option 5 and 12 are available unset everything except those two.

QUESTION Why doesnt the above work.

---

EDIT

So I tried simplifying it but I think I made it harder to understand.

This is a shipping loop. The available methods are ship:REGULAR_LOCAL, ship:EXPRESS_LOCAL, ship:PLAT_LOCAL, ship:REGULAR_INT, ship:EXPRESS_INT, ship:PLAT_INT, and FREE_SHIPPING [where LOCAL is within shipping country, and INT is international].

When an order goes over $100, FREE_SHIPPING automatically kicks in, but I also want to have either ship:EXPRESS_LOCAL or ship:EXPRESS_INT present depending on where the customer is from.

if( !strncmp($method_id,'ship:', 5) && ( ($method_id != 'ship:EXPRESS_LOCAL') || ($method_id != 'ship:EXPRESS_INT') ) )
    unset( $available_methods[ $method_id ] );

This should return with only FREE_SHIPPING, and either ship:EXPRESS_LOCAL or ship:EXPRESS_INT.

LOOP

if( isset( $available_methods['FREE_SHIPPING'] ) ) {
    foreach( $available_methods as $method_id => $method ) {
        if( !strncmp( $method_id, 'ship:', 5 ) && ( ($method_id != 'ship:EXPRESS_LOCAL') && ($method_id != 'ship:EXPRESS_INT') ) )
            unset( $available_methods[ $method_id ] );
    }
}   
return $available_methods;

Answer 1

Your updated question should contain the correct code already; this is how I would have written it:

$localOrInt = array('ship:EXPRESS_LOCAL', 'ship:EXPRESS_INT');

if (isset($available_methods['FREE_SHIPPING'])) {
    foreach ($available_methods as $method_id => $method) {
        if (!strncmp($method_id, 'ship:', 5) && !in_array($method_id, $localOrInt)) {
            unset($available_methods[$method_id]);
        }
    }
}