Question

The ever flaky Xdebug is on the fritz at the mo’ (normal service will be resumed as soon as possible), so I am reduced to “debug by echo”.

echo($path_info['filename'] . '    ' . $licence['issue_timestamp'].'<br>');      
if ($path_info['filename'] != $licence['issue_timestamp'])
{  
die('They are NOT equal');
   $_SESSION['error_messages'][] = 'This licence file has been copied';
   return False;
}
else   
die('They are equal');

outputs

1319266557_   1319266557
They are equal

Any idea what I am doing wrong? Is there something special about (trailing) underscores?

Answer 1

The docs state:

$a != $b Not equal TRUE if $a is not equal to $b after type juggling.

And that "type juggling" looks mighty suspicious. Elsewhere on that page, it mentions:

If you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically. These rules also apply to the switch statement. The type conversion does not take place when the comparison is === or !== as this involves comparing the type as well as the value.

And the example is a dead giveaway as to what’s happening in your case:

var_dump(100 == "1e2"); // 100 == 100 -> true

In terms of how strings are converted to integers, that can be seen here. The salient bit is (my bold):

If the string does not contain any of the characters ‘.’, ‘e’, or ‘E’ and the numeric value fits into integer type limits (as defined by PHP_INT_MAX), the string will be evaluated as an integer. In all other cases it will be evaluated as a float.

The value is given by the initial portion of the string.

Example: $foo = 1 + "10 Small Pigs"; // $foo is integer (11)

That’s why "123_" is equal to "123" ^(a). Bottom line, use !== since that ensures both the value and the type are the same.

---

^(a) See the online PHP executor: