strip替换为strip_tags，允许在sql中使用<，<=，> =，> - 正则表达式？

Question

I'm using wp-db.php on a non-Wordpress site which allows a apply_filters function to be used. I initially did this:

function apply_filters($type, $input) {
    return strip_tags($input);
}

I want to stop html from being saved. I thought I fixed the problem but then noticed that sql queries that included things like <= weren't working.

What I want it to do is to strip tags that begin with a character e.g. <b... but if there is a space or equals sign after the bracket e.g. < or <= then it shouldn't remove it.

I found this code but it doesn't work how I want it to:

preg_replace('/<[^>]*>/', '', $input);

e.g.

<b>test</b> abc <= def < ok? ilj >= xyz >

gets returned as:

test abc = xyz >

it should only remove <x...> where x is not a space or equals sign and remove </....>

BTW I noticed that < script> doesn't work so I think it's ok for < with a space after to stay.

Answer 1

Only the first tag is valid:

<b>1</b> <0b>2</0b> < b>3</ > <'b>4</'b> <(>5</(> <=>6</=>

This non-greedy regex removes the valid and closing tags:

/<[^(=\d' )].*?>/g

in php:

preg_replace('/<[^(=\d\' )].*?>/', '', $input);

See https://regex101.com/

I had those other tags due to sql like:

col1 < 10
col2 <10
col3 <'2010-10-10'
col4 <(SELECT col5...)
col5 <=20