将字符串计算为条件表达式

Question

I have an expression which looks like this:

$condition = "$foo>$bar";

and an array which has the values for the expression elements:

    array(
     'foo' => 3,
     'bar' => 4
    )

I did the replacement, in the $condition string using the str_replace() function, but the 3>4 expression returns true.

How can I properly evaluate my $condition expression in a if() statement?

Answer 1

I have no idea why you'd want to do this, but this is technically possible. Use extract() to import the variables from the array into the current scope. Once you have the variables, you can simply compare them as usual:

$values =array(
     'foo' => 3,
     'bar' => 4
);

extract($values);

$result = $foo > $bar;

if ($result) {
    echo '$foo is greater than $bar';
} else {
    echo '$foo is not greater than $bar';
}

---

If $condition is a string and you can't change it, you could use eval() to evaluate the expression first:

$condition = "$foo>$bar";
eval(sprintf('$result = %s;', $condition));

if ($result) {
    echo '$foo is greater than $bar';
} else {
    echo '$foo is not greater than $bar';
}