Missing Values

[iwato]

PROBLEM: Please consider the following two blocks of code. Each contains several echo statements; each returns a value indicating that the variable types of $return_same and $return_identical are boolean. When I go to display the value of $return_identical itself; however, nothing appears.

$return_same = ($bar == $foo);echo is_bool($return_same) . "<br />";echo var_dump($return_same) . "<br />";echo "$return_same <br /><br />";$return_identical = ($bar === $foo);echo is_bool($return_identical) . "<br />";echo var_dump($return_identical) . "<br />";echo "$return_identical <br /><br />";echo is_null($return_identical);

The output for the above two blocks of code is as follows:1bool(true) 1 1bool(false) QUESTION: With the exception of what is echoed for the var_dump() function, why is no value echoed for the $return_identical variable? Also, why is nothing displayed for the is_null() function?Roddy

[boen_robot]

a boolean false evaluates to an emptry string. This explains it all.

[iwato]

A boolean false evaluates to an emptry string. This explains it all.

Well, it explains a lot anyway.What it does not explain is the following. Can you?

<?php	$bar = "";	$foobar = "0";	if ($bar === $foobar) {		echo "The empty set and zero entered as a string are identical.<br />";	} else {		echo "The empty set and zero entered as a string are not identical.<br />";		if ($bar == $foobar) {			echo "The empty set and zero entered as a string are the same, but not identical.";		} else {			echo "This evaluation of the empty set and zero entered as a string is inconclusive.";		}	}?>

OUTPUTThe empty set and zero entered as a string are not identical.This evaluation of the empty set and zero entered as a string is inconclusive.Roddy

[dsonesuk]

can't see what problem is'$bar === $foobar' = same type (string) and same string value = FALSEecho "The empty set and zero entered as a string are not identical.<br />";'$bar == $foobar' = same string value = FALSE againecho "This evaluation of the empty set and zero entered as a string is inconclusive.";

[boen_robot]

The integer 0 is equivalent to the boolean false and the string "". The string "0" is not the same as the string "". Any string other than "" is equivalent to a boolean true.If you first cast the string "0" to an integer, and then to a boolean, you'll get a boolean false.See comparrison tables.

[justsomeguy]

To help clarify, since both of the arguments are strings it does not convert them, it compares the string values. If one of them was the number 0 or a boolean false then it would convert and the results would be different.

[iwato]

The integer 0 is equivalent to the boolean false and the string "". The string "0" is not the same as the string "". Any string other than "" is equivalent to a boolean true.If you first cast the string "0" to an integer, and then to a boolean, you'll get a boolean false.See comparrison tables.

The PHP Type Comparison Table will surely come in handy in the future.Thanks for making me aware of it.Roddy

[iwato]

To help clarify, since both of the arguments are strings it does not convert them, it compares the string values. If one of them was the number 0 or a boolean false then it would convert and the results would be different.

This was a very helpful clarification. No conversion.Roddy