strpos（）无法识别PHP字符串编码？

I have a binary Word .doc that looks something like this in string format:

þÿÿÿÿÿÿÿppp„±¶g œÙ Text in word doc here I'm interested in  [|`ñÿ|Standard1$S_HmHnHsHtHOJPJQJCJEH567>

When I echo that string, I can see all the text I'm interested in finding in between unrecognized characters (but those I'm not worried about them since I only want the text). The issue is that PHP does not seem to recognize it as a string and so I cannot search it with strpos(), strpos(), strchr(), mb_strpos() all return nothing. No -1, no error in the PHP error log, just nothing.

However, when I call gettype() I get string. I suspect this is an encoding issue, but mb_detect_encoding returns UTF-8. I have tried converting it to multiple different encoding types, without avail.

How can I get PHP to search this string? I understand that parsing a Word .doc is more complex of an issue, but for my purposes the plaintext I'm interested in are in the binary data. Does anyone have any experience with this?

Thank you :)

Notice the part "Standard1$". php is taking $ as the operator instead of a character. check here.

<?php

$s = "þÿÿÿÿÿÿÿppp„±¶g œÙ Text in word doc here I'm interested in  [|`ñÿ|Standard1$S_HmHnHsHtHOJPJQJCJEH567>";

$s2 = strpos($s, "interested");
echo $s2;
?>

you might want to put a backslash before that $ sign.

Since you string seems binary encoded and you are only interested in text a quick solution would be to use filter_var to clean the string from non ascii-printable characters.Try using this before searching:

$clean_string = filter_var($str,FILTER_FLAG_STRIP_LOW, FILTER_FLAG_STRIP_HIGH);