javascript to check O (zero) is in decimal format

I've been having a little problem with one of my input boxes in a form .  It seems that my code doesn't like '0' being entered.  Zero does not equate to '0.00' in PHP and this must be throwing an error somewhere. 

However other number are fine; like '1' does not need to be entered as '1.00' . 

php 0 to 0.00 conversion problems

php 0 does not equal 0.00

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The quickest way to solve this problem for me was to write a bit of javascript takes that input box - and if the entered value is '0' - then change it to '0.00'  .  Here's the code.

var x=document.forms["myForm2"]["hourly_rate"].value;
if (x==0)
  {
  document.forms["myForm2"]["hourly_rate"].value='0.00';
  return;
  }


with the form being something like

< form name="myForm2" method="post">
Hourly Rate* :
< /form>