Find the position of the first occurrence of a case-insensitive substring in a string
stripos ( string $haystack , mixed $needle [, int $offset = 0 ] ) : int
The string to search in.
Note that the needle may be a string of one or more characters. If needle is not a string, it is converted to an integer and applied as the ordinal value of a character. This behavior is deprecated as of PHP 7.3.0, and relying on it is highly discouraged. Depending on the intended behavior, the needle should either be explicitly cast to string, or an explicit call to chr() should be performed.
If specified, search will start this number of characters counted from the beginning of the string. If the offset is negative, the search will start this number of characters counted from the end of the string.
Returns the position of where the needle exists relative to the beginnning of the haystack string (independent of offset). Also note that string positions start at 0, and not 1. Returns FALSE if the needle was not found.
Warning: This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. Please read the section on Booleans for more information. Use the identity operator (===) for testing the return value of this function.
offset | Negative
offset | Non-negative