这可以在没有评估的情况下完成吗？ （注意：表达式确实来自一个字符串）

In PHP I can wanting to eval a string, which might call one of my user defined methods.

What I have is something like:

function convertToBytes($value)
{
    $number=substr($value,0,-1);
    switch(strtoupper(substr($value,-1))){
        case "K":
            return $number*1024;
        case "M":
            return $number*pow(1024,2);
        case "G":
            return $number*pow(1024,3);
        case "T":
            return $number*pow(1024,4);
        case "P":
            return $number*pow(1024,5);
        default:
            return $value;
    }
} 

$expression = 'if (convertToBytes("1024K") >= 102400)
    return true;
else 
    return false;';

$value = eval($expression);

I am wondering if I can do that without the use of an eval.

I'm confused. You shouldn't ever have to use eval() for something like this, when you can easily set $value to the real boolean value such as:

$value = (convertToBytes("1024K") >= 102400);

Your best bet it splitting it up. So that it is infact something like this:

function convertToBytes($value, $type) {
 ...
}

so then you can do:

$value = (convertToBytes(1024, 'K') >= 102400);

Yourfunction would look like:

function convertToBytes($value, $type = "K")
{
    switch($type){
        case "K":
            return $value*1024;
        case "M":
            return $value*pow(1024,2);
        case "G":
            return $value*pow(1024,3);
        case "T":
            return $value*pow(1024,4);
        case "P":
            return $value*pow(1024,5);
        default:
            return $value;
    }
}