String -> Number Automatic Conversion

I am not sure if this is a bug or I am just doing something dumb but I am having a problem with automatic converting of strings to a number between 0 and -1. For example: $p1 = Array ( 0 => "-.15", 1 => "-.15" + 0, 2 => (float) "-.15" + 0, 5 => "-1.15", 6 => "-1.15" + 0, 7 => (float) "-1.15" + 0, 8 => ".15", 9 => ".15" + 0, 10 => (float) ".15" + 0, 11 => "1.15", 12 => "1.5" + 0, 13 => (float) "1.5" + 0 ); If I print $p1 I get: Array ( [0] => -.15 [1] => 0 [2] => -0.15 [5] => -1.15 [6] => -1.15 [7] => -1.15 [8] => .15 [9] => 0.15 [10] => 0.15 [11] => 1.15 [12] => 1.5 [13] => 1.5 ) Note that the results for element [1] is 0 not -.15 as I had expected. It does not matter what value is added to the string. Any value outside the range of -1 < value < 0 gives the correct results. Is this a bug or am I missing something. Thanks for any help, Art Nuzzo