in_array returns true if needle is 0

Question

I have an issue with in_array function. Test below returns true:

in_array(0, array('card', 'cash'))

How is it impossible, how can I prevent it ?

However

in_array(null, array('card', 'cash'))

returns false.

LOOSE TYPING... you're comparing number with string, so the string is converted to a number, giving 0 in this case, and 0 == 0. Use the optional STRICT argument — Mark Baker, May 28 '13 at 08:54

ThiefMaster · Accepted Answer · 2013-05-28T08:59:27.423

24

Casting any string that doesn't start with a digit to a number results in 0 in PHP. And this is exactly what happens when comparing 0 with some string. See the PHP docs for details about how comparisons between various types are done.

Use the third argument (set it to true) of in_array to avoid loose type comparison.

in_array(0, array('card', 'cash'), true) === false

edited May 28 '13 at 08:59

answered May 28 '13 at 08:53

ThiefMaster

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All right, that's the answer that I need. Thank you ! – hsz May 28 '13 at 08:55

score 7 · Answer 2 · answered May 28 '13 at 08:58

7

when you compare in in_array string is converted to int while comparing incompatible data types it means cashor card is converted to 0

This is all because of type casting

You have 2 options

1 . Type casting

in_array(string(0), array('card', 'cash'))) === false;

2 .Use third parameter on in_array to true which will match the datatypes

in_array(0, array('card', 'cash'), true) === false;

see documentation

answered May 28 '13 at 08:58

alwaysLearn

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OOPS !! bit late to answer that .. – alwaysLearn May 28 '13 at 08:59

score 2 · Answer 3 · answered May 28 '13 at 08:59

You can prevent it by using the 'strict' parameter:

var_export(in_array(0, array('card', 'cash'), true));

var_export(in_array(null, array('card', 'cash'), true));

returns false in both cases.

From the docs to in_array()

If the third parameter strict is set to TRUE then the in_array()
function will also check the types of the needle in the haystack.

score 0 · Answer 4 · answered May 28 '13 at 08:53

0

An answer can be casting 0 to string, so:

in_array((string) 0, array('card', 'cash'))

Keep in mind that 0 can be some variable, so casting can be helpful.

answered May 28 '13 at 08:53

hsz

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in_array returns true if needle is 0

4 Answers4