PHP in_array() / array_search() odd behaviour

Question

I have found some odd behaviour while I was using the PHP function in_array(). I have an array like this:

$arr = [TRUE, "some string", "something else"];

Now if I want to check if "test" is in the array it is clearly not, but in_array() still returns TRUE, why is that?

$result = in_array("test", $arr);
var_dump($result);  //Output: bool(true)

The same thing happens when using array_search():

$result = array_search("test", $arr);
var_dump($result);  //Output: int(0)

I thought maybe that the value TRUE in the array was automatically causing the function to return TRUE for every result without checking the rest of the array, but I couldn't find any documentation that would suggest that very odd functionality.

Can you provide a more complete code example? The code you posted is not very helpful. You might have just made an assignment mistake or whatever... — Felix Kling
– Felix Kling, Commented Apr 29, 2010 at 17:33
The results variable is assigned the line before the checks are run. Then I added the die(var_dump($results)) after that line to see what array it was returning. — animuson
– animuson ♦, Commented Apr 29, 2010 at 17:35

Community · Accepted Answer · 2017-05-23 12:33:45Z

13

This behaviour of the function in_array() and array_search() is not a bug, but instead well documented behaviour.

Both functions have a 3rd optional parameter called $strict which by default is FALSE:

bool in_array ( mixed $needle , array $haystack [, bool $strict = FALSE ] )

mixed array_search ( mixed $needle , array $haystack [, bool $strict = false ] )

Now what that means is that by default both functions use loosely(==) comparison to compare the values. So they only check if the values are the same after PHP type juggling and without checking the type. Because of that in your example TRUE == "any none emtpy string" evaluates to TRUE.

So by setting the 3rd parameter to TRUE while calling the function you say that PHP should use strict(===) comparison and it should check value AND type of the values while comparing.

See this as a reference: How do the PHP equality (== double equals) and identity (=== triple equals) comparison operators differ?

edited May 23, 2017 at 12:33

CommunityBot

11 silver badge

answered Apr 29, 2010 at 17:37

Fletcher Moore

13.9k11 gold badges43 silver badges59 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Maciek Over a year ago

I had a situation where my in_array was accepting almost any variable using python script posting into a php script. Very unusual but this fixed it.

Felix Kling · Accepted Answer · 2010-04-29 17:41:16Z

3

You are right, the boolean can indeed cause this. Set the strict flag in the in_array function, this way also the type of the element is checked (basically the same as using ===):

if (in_array("username", $results, true)) // do something
if (in_array("password", $results, true)) // do something
if (in_array("birthday", $results, true)) // do something

answered Apr 29, 2010 at 17:41

Felix Kling

820k181 gold badges1.1k silver badges1.2k bronze badges

Collectives™ on Stack Overflow

PHP in_array() / array_search() odd behaviour

2 Answers 2

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related