how to check for characters in a string php code example

Example 1: if text contains word then in php

if (strpos($haystack,$needle) !== false) {
    echo "$haystack contains $needle";
}

Example 2: php check if string contains a char

$haystack = 'This is my haystack that we shall check'
$has_A = strpos($haystack, 'A') !== false;
$has_a = strpos($haystack, 'a') !== false;