php - using strpos() to replace multiple comparisons in an if statement

Question

Is it OK to replace multiple comparisons by using strpos()?
Example:
changing

if ( $linecounter == $extra1 || $linecounter == $extra2 || $linecounter == 5 )
{ 
  ...
}

to

$ok = ' ' . $extra1 . $extra2 . '5';
if ( strpos($ok, $linecounter) > 0 )
{
  ...
}

Answer 1

No, it's not OK because that's not what strpos is for. It's easy to find problematic examples in the general case (e.g. $linecounter == 15 and $extra2 == 1 -- the strpos check will succeed when it should not have).

If you want to lose the separate conditions so much, workable alternatives would be either a switch statement or in_array:

switch($linecounter) {
    case $extra1: case $extra2: case 5:
        // whatever
        break;
}

if (in_array($linecounter, [$extra1, $extra2, 5])) {
    // whatever
}

As an aside, using strpos with a greater-than-zero test like that is not good style. What you want to say is "if it's found in the string", so write exactly that and lose the "prefix a space" hack:

if ( strpos($extra1 . $extra2 . '5', $linecounter) !== false )