(PHP 5, PHP 7, PHP 8)
strripos — Find the position of the last occurrence of a case-insensitive substring in a string
$haystack, string $needle, int $offset = 0): int|false
   Find the numeric position of the last occurrence of
   needle in the haystack string.
  
Unlike the strrpos(), strripos() is case-insensitive.
haystackThe string to search in.
needle
  Prior to PHP 8.0.0, if needle is not a string, it is converted
  to an integer and applied as the ordinal value of a character.
  This behavior is deprecated as of PHP 7.3.0, and relying on it is highly
  discouraged. Depending on the intended behavior, the
  needle should either be explicitly cast to string,
  or an explicit call to chr() should be performed.
 
offset 
       If zero or positive, the search is performed left to right skipping the
       first offset bytes of the
       haystack.
      
       If negative, the search is performed right to left skipping the
       last offset bytes of the
       haystack and searching for the first occurrence
       of needle.
       
Note:
This is effectively looking for the last occurrence of
needlebefore the lastoffsetbytes.
   Returns the position where the needle exists relative to the beginnning of
   the haystack string (independent of search direction
   or offset).
   
Note: String positions start at 0, and not 1.
   Returns false if the needle was not found.
  
This function may
return Boolean false, but may also return a non-Boolean value which
evaluates to false. Please read the section on Booleans for more
information. Use the ===
operator for testing the return value of this
function.
| Version | Description | 
|---|---|
| 8.2.0 | Case folding no longer depends on the locale set with setlocale(). Only ASCII case folding will be done. Non-ASCII bytes will be compared by their byte value. | 
| 8.0.0 | Passing an int as needleis no longer supported. | 
| 7.3.0 | Passing an int as needlehas been deprecated. | 
Example #1 A simple strripos() example
<?php
$haystack = 'ababcd';
$needle   = 'aB';
$pos      = strripos($haystack, $needle);
if ($pos === false) {
    echo "Sorry, we did not find ($needle) in ($haystack)";
} else {
    echo "Congratulations!\n";
    echo "We found the last ($needle) in ($haystack) at position ($pos)";
}
?>
The above example will output:
Congratulations! We found the last (aB) in (ababcd) at position (2)