== operator for string

Question

Why does this code echo Yes. even though variables are not equal!

$a = '0e462097431906509019562988736854';
$b = '0e830400451993494058024219903391';

if( $a == $b ) echo 'Yes.';
else echo 'No!';

check answers here: http://stackoverflow.com/questions/14259162/comparing-different-strings-in-php-with-returns-true — Dyrandz Famador, Mar 09 '15 at 05:12
PHP is clever/stupid enough to decide that they're hexadecimal numbers I believe. The int type probably doesn't carry that much precision on your machine (so they overflow), and the resulting values are considered equal. — alex, Mar 09 '15 at 05:12
And lots of similar/related questions: [strcmp vs. == vs. === in PHP for checking hash equality](http://stackoverflow.com/q/14711474), [How do the PHP equality (== double equals) and identity (=== triple equals) comparison operators differ?](http://stackoverflow.com/q/80646), [Comparing String to Integer gives strange results](http://stackoverflow.com/q/672040), [Why does PHP consider 0 to be equal to a string?](http://stackoverflow.com/q/6843030) — mario, Mar 09 '15 at 06:04

score 8 · Answer 1 · edited May 23 '17 at 10:27

8

Both will treated as numbers, and PHP had limitations in number storage before. So check that.

Try to use '==='. it will check the type also, so those will not convert to numbers.

Refer this question and its answers.

edited May 23 '17 at 10:27

Community

answered Mar 09 '15 at 05:11

arun

score 2 · Answer 2 · answered Mar 09 '15 at 05:07

2

You want strcmp, not the equality operator.

answered Mar 09 '15 at 05:07

score 2 · Answer 3 · answered Mar 09 '15 at 05:11

2

try it, with using strcmp function:

if(int strcmp ($a,$b)===0) echo 'Yes.';
else echo 'No!';

answered Mar 09 '15 at 05:11

Pavel Shamparov

score 1 · Answer 4 · answered Mar 09 '15 at 06:03

1

Try using '===' instead of '=='.

'==' has a "weaker" comparison because it does not check for type.

'===' on the other hand, checks for the type as well, and it is generally good practice to be more explicit when you compare two things.

answered Mar 09 '15 at 06:03

tzhenghao

4 Answers4