PHP比较两个值？

While comparing the values in the below array

array
  0 => 
    array
      0 => string '09:30' (length=5)
      1 => string '11:00' (length=7)
  1 => 
    array
      0 => string '11:01' (length=5)
      1 => string '18:00' (length=7)
  2 => 
    array
      0 => string '12:05' (length=5)
      1 => string '14:00' (length=7)
  3 => 
    array
      0 => string '14:00' (length=5)
      1 => string '20:20' (length=7)

If I am using if($a > $b) it is even giving true for equal values ($a = $b) // this is not comparision , while if($a - $b > 0) is giving accurate result.

Why so ?

EDIT: The code part where I am using cmp.

This woks fine

for($i=0; $i < $fr -1 ; $i++)
{
    if( $dtime[$i][1] - $dtime[$i+1][0] > 0 )
    {
        echo 'It is clashing';
        break;
    }
}

This does not works fine

for($i=0; $i < $fr -1 ; $i++)
{
    if( $dtime[$i][1] > $dtime[$i+1][0] )
    {
        echo 'It is clashing';
        break;
    }
}

Though the way you're doing comparisons seems odd, I think you have a data cleaning problem. In the top part of your question it appears you're doing a var_dump(). Notice how'09:30' (length=5) is correct but '11:00' (length=7) is wrong because the length should be 5 also. There are some additional hidden characters (maybe or ) at the beginning or end of the data.

To fix, try running $value = trim($value) on each of your array elements before comparing.