diff --git a/language/types/float.xml b/language/types/float.xml
index 2fc22d25b1..0230d987d7 100644
--- a/language/types/float.xml
+++ b/language/types/float.xml
@@ -66,10 +66,10 @@ EXPONENT_DNUM [+-]?(({LNUM} | {DNUM}) [eE][+-]? {LNUM})
   </para>
 
   <para>
-   So never trust floating number results to the last digit, and never compare
-   floating point numbers for equality. If higher precision is necessary,
-   the <link linkend="ref.bc">arbitrary precision math functions</link> and
-   <link linkend="ref.gmp">gmp</link> functions are available.
+   So never trust floating number results to the last digit, and do not compare 
+   floating point numbers directly for equality. If higher precision is
+   necessary, the <link linkend="ref.bc">arbitrary precision math functions</link>
+   and <link linkend="ref.gmp">gmp</link> functions are available.
   </para>
  </warning>
 
@@ -88,6 +88,43 @@ EXPONENT_DNUM [+-]?(({LNUM} | {DNUM}) [eE][+-]? {LNUM})
   </para>
 
  </sect2>
+
+ <sect2 xml:id="language.types.float.comparison">
+  <title>Comparing floats</title>
+
+  <para>
+   As noted in the warning above, testing floating point values for equality is
+   problematic, due to the way that they are represented internally. However,
+   there are ways to make comparisons of floating point values that work around
+   these limitations.
+  </para>
+
+  <para>
+   To test floating point values for equality, an upper bound on the relative
+   error due to rounding is used. This value is known as the machine epsilon,
+   or unit roundoff, and is the smallest acceptable difference in calculations.
+  </para>
+  
+  <informalexample>
+   <simpara>
+    <varname>$a</varname> and <varname>$b</varname> are equal to 5 digits of
+    precision.
+   </simpara>
+   <programlisting role="php">
+<![CDATA[
+<?php
+$a = 1.23456789;
+$b = 1.23456780;
+$epsilon = 0.00001;
+
+if(abs($a-b) < 0.00001) {
+    echo "true";
+}
+?>
+]]>
+   </programlisting>
+  </informalexample>
+ </sect2>
  
  <sect2 xml:id="language.types.float.nan">
   <title>NaN</title>