The example below will output "Word NOT found", even though the word was actually found.

$str = "This is a test";
$pos = strpos($str, "This");

if ($pos)
	echo "Word found";
else
	echo "Word NOT found";


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This example outputs the proper results, thanks to type checking (Word found)

$str = "This is a test";
$pos = strpos($str, "This");

if ($pos === false)
	echo "Word NOT found";
else
	echo "Word found";