实现strstr

Returns the index of the first occurrence of needle in haystack, or -1
if needle is not part of haystack.

实现代码如下：

function strstr1($haystack, $needle) {    $len1 = strlen($haystack);    $len2 = strlen($needle);    if ($len1 < 1 || $len2 < 1 || $len1 < $len2)        return -1;    $len = $len1 - $len2;    for ($i = 0; $i <= $len; $i++) {        if (substr($haystack, $i, $len2) == $needle) {            return $i;            //return substr($haystack, $i); // PHP函数        }    }    return -1;}echo strstr1('abcde', 'b');