check substring in php

$myString = 'Hello Bob how are you?';
if (strpos($myString, 'Bob') !== false) {
    echo "My string contains Bob";
}$a = 'Hello world?';

if (strpos($a, 'Hello') !== false) { //PAY ATTENTION TO !==, not !=
    echo 'true';
}
if (stripos($a, 'HELLO') !== false) { //Case insensitive
    echo 'true';
}$result = strpos("haystack", "needle");

if ($result != false)
{
  // text found
}if (strpos($haystack,$needle) !== false) {
    echo "$haystack contains $needle";
}// returns true if $needle is a substring of $haystack
function contains($haystack, $needle){
    return strpos($haystack, $needle) !== false;
}