Why use !== FALSE to check stripos in php?

Question

Here is the code I am looking at.

foreach ($header as $idx => $field) {
    if (stripos($field, 'foo') !== false) {
        $cols['foo'] = $idx;
    } else if (stripos($field, 'bar') !== false) {
        $cols['bar'] = $idx;
    } else if (stripos($field, 'brr') !== false) {
        $cols['brr'] = $idx;
    } else if (stripos($field, 'ffo') !== false) {
        $cols['ffo'] = $idx;
    }
}

Sorry, don't know how to format the code prettily either, any tips on that would be appreciated.

I am looking at some code written by someone much smarter than I, so I am not inclined to trust my first impression to just change everything to if(stripos($foo)), but why do it this way?

Answer 1

The answer is that in PHP a "false" value can be satisfied by a handful of values, such as an empty array, an empty string, a NULL, integer 0, etc. See the empty() function page for a full list:

http://php.net/empty

So this would always yield incorrect results:

if(strpos("abc", "a")) { 
  echo "Yes";
} else {
  echo "No";
}

Since the "a" occurs at the first position (index 0) then PHP considers "if (0)" to be false.

When strpos does NOT find the needle in your haystack it will return the boolean FALSE, which is what you want to check with the triple-equal operator which checks both type and value. See the docs on comparison operators

http://www.php.net/manual/en/language.operators.comparison.php

Answer 2

stripos returns the position of a string inside another, and if the string is not found, it returns false, so it's recommended to use the identity comparison operators (===, !==), because PHP considers 0 as a "falsy" value, consider this example:

// Find the position of the 'a' character in the 'abc' string:
stripos('abc', 'a') !== false; // true, position is 0
stripos('abc', 'a') != false; // false, 0 is "falsy"