Why Does PHP's `in_array()` and `array_search()` Sometimes Return Unexpected Results?

PHP in_array() and array_search() Peculiar Behavior: Delving into the Optional Parameter

In using PHP's in_array(), you may encounter unexpected behavior when searching for non-existent elements. This article investigates this oddity and explores the resolution by introducing the obscure $strict parameter.

Consider an array like $arr = [TRUE, "some string", "something else"]. Upon searching for "test" using in_array(), it surprisingly returns TRUE. Similarly, array_search() retrieves an "inaccurate" index of 0. This behavior initially appears puzzling, leading to the assumption that TRUE automatically triggers a universalized positive result.

However, this is not a bug but an intentional feature. Both in_array() and array_search() have an often-overlooked third parameter, $strict, which determines the comparison mode. Its default value, FALSE, allows for loose (==) comparison, ignoring type discrepancies.

Consequently, in the case of $arr, TRUE == "any non-empty string" evaluates to TRUE. By setting $strict to TRUE, you instruct PHP to employ strict (===) comparison, verifying both value and type equality.

This knowledge brings clarity to the perplexing behavior. By employing strict comparison, you can avoid misinterpretations and ensure accurate search results. For further insights into equality and identity comparison in PHP, consult the reference provided.

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