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";