PHP false negative with == on strings

Question

There are lots of examples of false positives when using == to compare two strings in PHP.

For example, '1' == '1.0' is true.

However, are there any false negatives? Is there some string $a such that $a == $a is false due to type juggling?

if you want avoid some false positive use strict compare '1' === '1.0' so you compare type and value and not only value — ScaisEdge
– ScaisEdge, Commented Feb 26, 2017 at 20:45
Or you can use strcmp() and strcasecmp() to compare string. — frz3993
– frz3993, Commented Feb 26, 2017 at 20:47
Is that a typo? Or are you really looking for a string that is not equal to itself? Because no, there is no situation in PHP where $a == $a would ever evaluate to false. — AmericanUmlaut
– AmericanUmlaut, Commented Feb 26, 2017 at 20:50
I'm sorry, but a string comparison from "1.0" == "1" is not true. If you want to compare the values of the strings, you need to convert them to numeric values before or during the test: if (floatval('1') == floatval('1.0')) would be true, as it is comparing the correct types. Read about type juggling: php.net/manual/en/language.types.type-juggling.php — R. Smith
– R. Smith, Commented Feb 26, 2017 at 21:31

Community · Accepted Answer · 2017-05-23 12:00:31Z

1

No, php will not provide false negatives. php will create false positives via type juggling as a feature (it tries to help).

1 Answer 1