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, Feb 26 '17 at 20:45
Or you can use `strcmp()` and `strcasecmp()` to compare string. — frz3993, Feb 26 '17 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, Feb 26 '17 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: http://php.net/manual/en/language.types.type-juggling.php — R. Smith, Feb 26 '17 at 21:31
PHP will still type juggle even if both inputs are already strings. `var_dump('1.0' == '1')` => `bool(true)`, but `var_dump('1.0' === '1')` => `bool(false)` — Nick Frost, Feb 26 '17 at 21:36

score 1 · Accepted Answer · edited May 23 '17 at 12:00

1

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

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