Check if string exists php

- Php check if string exists in text
- Check if word exists in string php
- Check if substring exists in string php
- Check if character exists in string php
- Check if value exists in string php
- Php regex to check if string exists
- Php check if part of string exists
- Check if string exists in array php
- Php check if string exists in file
- Check if comma exists in string php
- Php check if string already exists
- Php check if substring exists
- Check if value exists in comma separated string php
- Php check if query string parameter exists