Description:
------------
When I convert a large float value to a string and then back to a float, the original and the resulting values are not equal.

Note: I looked for this error in the bug list, but did not find one with the current stable release of PHP (4.3.3).

Thanks in advance.

Reproduce code:
---------------
	// Create some large number
	$testStart = (float) unserialize("d:1125899906842624;");	
	// Output value
	echo "Before string conversion: $testStart <br>\n";
	// Convert value to string
	$testString = (string) $testStart;	
	// Output string
	echo "After string conversion: $testString <br>\n";
	// Convert string back to a value
	$testEnd = (float) $testString;	
	// Output value
	echo "After float conversion: $testEnd <br>\n";	
	// Compare the two values
  	if( $testStart == $testEnd ) {
		echo "<br>\nThe two values are equal.<br>\n";
  	} else {
		echo "<br>\nThe two values appear to be the same, but are <u>not</u> equal!<br>\n";
	};

Expected result:
----------------
I expect to see "The two values are equal."

Actual result:
--------------
I am getting "The two values appear to be the same, but are not equal!"