PHP中的逻辑问题

Question

Ok, i tested what follows and i'll just let you know what i discovered:

echo ('-1' < 0) ? 'true' : 'false'; // will echo "true"
echo ('1' > 0) ? 'true' : 'false'; // will echo "true"
# Notice that '-1' and '1' are strings

Now let's take an array, coming from the database after filtering all the result in order to get only rows with UID = 1.

$this->a = array(
    [0] => array(
        'UID' => '1',
        'PID' => '91',
        'Amount' => '-1'
    ),
    [1] => array(
        'UID' => '1',
        'PID' => '92',
        'Amount' => '1'
    ),
    [2] => array(
        'UID' => '1',
        'PID' => '93',
        'Amount' => '1'
    )
);

Now i want to create a function posAmount($PID) that returns true if 'Amount' > 0 or false if 'Amount' < 0. (Notice: Amount = 0 is something i don't really care). Also i'd like to write as similar function called negAmount($PID) that returns the exactely opposite of the first. I'd like, now, to introduce you to my twin functions:

public function posAmount($pid)
{
    foreach ($this->a as $a)
    {
        if (count($this->a) == 0) { return false; }
        return ($a['PID'] == $pid and $a['Amount'] > 0) ? true : false;
    }
}

public function negAmount($pid)
{
    foreach ($this->a as $a)
    {

        if (count($this->a) == 0) { return false; }
        return ($a['PID'] == $pid and $a['Amount'] < 0) ? true : false;
    }
}

The cool fact is that, regarding the first array (which, i checked with var_dump() keeps its nature trough the entire script):

$istance->negAmount(91); // Returns true, as expected
$istance->posAmount(92); // Returns false, as NOT expected.
# Why do God wants me to get mad?

Answer 1

The problem is that you are always returning on the first iteration of the foreach loop. You should rewrite the functions like this:

public function negAmount($pid) {
    if (count($this->a) == 0) { return false; }
    foreach ($this->a as $a) {
        if ($a['PID'] == $pid) {
            if ($a['Amount'] < 0) {
                return true;
            }
        }
    }
    return false;
}

public function posAmount($pid) {
    if (count($this->a) == 0) { return false; }
    foreach ($this->a as $a) {
        if ($a['PID'] == $pid) {
            if ($a['Amount'] > 0) {
                return true;
            }
        }
    }
    return false;
}