This function is used for binary safe comparison of two strings from an offset, up to length characters.

    substr_compare(string1,string2,startpos,length,case)

In the above syntax "string1" ,"string2" are the strings to compare, "startpos" specifies from where to compare string1,"length" specifies how much of string1 to compare, "case" specifies comparison is case sensitive or case insensitive.The function returns "0" if both string are equal, returns a value "<0" if string1 is less than string2, returns a value "0>" if string1 is greater than string2.

    <?php
    echo substr_compare("abcde","bc", 1, 2); 
    ?>

    0

In the above example the string "bc" are compared for two places "abcde" since its equal returns "0".