Error : Warning: strpos() [function.strpos]: Offset not contained in string - can not find solution

Question

I know, this question has been asked, but unfortunately, there are no answers how to solve this problem.

This appears in my logfiles:

PHP message: PHP Warning: strpos(): Offset not contained in string in ... on line 479

Unfortunately, I can not understand what causes this problem and how to fix it. I tested this function many times (with large $text, with short $text, with $spam words and without $spam words) but I never get this error. So, what kind of texts my users submit that cause this error?

    if (strposab($text, $spam, 1)) {
    echo "Email addresses and URLs not allowed here";
die;
    }

$spam = array('http','www','hotmail','yahoo','gmail','msn');


function strposab($haystack, $needles=array(), $offset=0) {
$chr = array();
foreach($needles as $needle) {
$res = strpos($haystack, $needle, $offset);
if ($res !== false) $chr[$needle] = $res;
}
if(empty($chr)) return false;
return min($chr);
} 

Second question:

For some reason this function does not filter the first word of the string. For example in this string function does not find word "hotmail":

$text = 'hotmail test test test test';

but in this string it finds word " hotmail":

$text = 'test hotmail test test test test';

Answer 1

The offset value is higher than the length of the string to search in.

Answer 2

To the first question:

Most likely at one point you're passing an empty string to your function. Offset in the strpos call indicates from which character it should start searching for $needle. It's 0-based, so if you want to start from the absolute beginning, you either set it to 0 or omit it (it defaults to 0.)

To the second question:

As mentioned before, the offset is 0-based, so if $needle you're searching for is exactly in the beginning of $haystack, it cannot be found if $offset is 1. With $offset = 1 it would be as if you're searching in a string that looks like this: 'otmail test test test test'.

One more thing:

I suggest you should use stripos, not strpos for your purposes, as it is case-insensitive and will also find words with uppercase letters, if it's something you might need.