Binary safe comparison of two strings from an offset, up to length characters
substr_compare ( string $main_str , string $str , int $offset [, int $length [, bool $case_insensitivity = FALSE ]] ) : int
The main string being compared.
The secondary string being compared.
The start position for the comparison. If negative, it starts counting from the end of the string.
The length of the comparison. The default value is the largest of the length of the str compared to the length of main_str minus the offset.
If case_insensitivity is TRUE, comparison is case insensitive.
Returns < 0 if main_str from position offset is less than str, > 0 if it is greater than str, and 0 if they are equal. If offset is equal to (prior to PHP 7.2.18, 7.3.5) or greater than the length of main_str, or the length is set and is less than 0, (or, prior to PHP 5.5.11, less than 1) substr_compare() prints a warning and returns FALSE.
main_str str offset | Negative
main_str str offset | Non-negative