Dynamically select a comparison operator (>=, <=, etc) in a conditional?

if (foo >= bar) baz();

But let's say sometimes baz(); needs to be run when foo <= bar, or foo == bar... and let's say that this comparison opera开发者_Go百科tor is grabbed from, say, a db table, and placed into a variable: $param = ">=".

Is there any way you could modify the first line to use $param, besides a switch-case with multiple if statements?

In my code, baz(); spans about a whole bunch of lines, and would become an organizational nightmare were I to manage it by hand.

function lt($a, $b)
{
  return $a < $b;
}

 ...

$relops = Array(
  '<' => 'lt',
   ...
);

echo $relops['<'](2, 3);

I solved this using:

function doComparison($a, $operator, $b)
{
    switch ($operator) {
        case '<':  return ($a <  $b); break;
        case '<=': return ($a <= $b); break;
        case '=':  return ($a == $b); break; // SQL way
        case '==': return ($a == $b); break;
        case '!=': return ($a != $b); break;
        case '>=': return ($a >= $b); break;
        case '>':  return ($a >  $b); break;
    }

    throw new Exception("The {$operator} operator does not exists", 1);
}

Use eval()?

$param = ">=";
eval ("if (foo $param bar ) baz();");

Read more on the documentation page for the eval function.

EDIT:

Indeed, as others have mentioned, if there are alternatives, they are almost always better than eval(). If used, it must be used with care.

elaborating on my comment:

function variableOpComparison($v1, $v2, $o) {
    if ($o == '!=') return ($v1 != $v2); // could put this elsewhere...
    $operators = str_split($o);
    foreach($operators as $operator) {
        switch ($operator) { // return will exit switch, foreach loop, function
            case '>': if ($v1 > $v2) return true; else continue; break;
            case '<': if ($v1 < $v2) return true; else continue; break;
            case '=': if ($v1 == $v2) return true; else continue; break;
            default: throw new Exception('Unrecognized operator ' . $operator . ' in ' . $o);
        }
    }
    return false;
}