CODEWITHSUNDEEP
phpstrpos
DreamWave
DreamWave

Reputation: 1940

Loosely checking the return value from strpos() gives unintended result

I'm using strpos() to find the position of a string in another string. I first check if the string is found at all in there. Here's my line:

if (
    strpos($grafik['data'], $ss1) <> false
    && strpos($grafik['data'], $ss2) <> false
    && strpos($grafik['data'], $ss1) < strpos($grafik['data'],$ss2)
)

I check if both strings are contained and then I want the first one to be placed before the second one. In the PHP manual it says that strpos() returns false when string is not found. However if my string starts at the zero position (strpos() returns 0 since its the beginning), it seems like this statement

strpos($grafik['data'], $ss1) <> false

is false. Somehow 0 is equal to false! How do I make the statement true when strpos() returns 0?

Upvotes: 6

Views: 8542

Answers (3)

user965748
user965748

Reputation: 2397

This function behaves unpredictably, so to be sure it'll have deterministic behavior use either 

if(strpos($text,$string)===false)

or test it using a variable

$pos=strpos($text,$string); if($pos===false)

Upvotes: 4

pinaki
pinaki

Reputation: 5473

You need to check with ===. This will make sure you have exact false and not 0.

Upvotes: 5

Lekensteyn
Lekensteyn

Reputation: 66525

From http://www.php.net/manual/en/function.strpos.php:

Warning

This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or "". Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.

You have to use the === operator instead of ==.

In your case, instead of using <>, use !==:

strpos($grafik['data'], $ss1) !== false

This will return TRUE if $ss1 is found in $grafik['data']

Upvotes: 18

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