(PHP 8)
str_contains — Determine if a string contains a given substring
   Performs a case-sensitive check indicating if needle is contained
   in haystack.
  
haystackThe string to search in.
needle
       The substring to search for in the haystack.
      
Example #1 Using the empty string ''
<?php
if (str_contains('abc', '')) {
    echo "Checking the existence of the empty string will always return true";
}
?>The above example will output:
Checking the existence of the empty string will always return true
Example #2 Showing case-sensitivity
<?php
$string = 'The lazy fox jumped over the fence';
if (str_contains($string, 'lazy')) {
    echo "The string 'lazy' was found in the string\n";
}
if (str_contains($string, 'Lazy')) {
    echo 'The string "Lazy" was found in the string';
} else {
    echo '"Lazy" was not found because the case does not match';
}
?>The above example will output:
The string 'lazy' was found in the string "Lazy" was not found because the case does not match
Note: This function is binary-safe.