- print_r: documentation ( source)
- preg_match_all: documentation ( source)
- array_unique: documentation ( source)
<?php
$str = "cao isso pala só temp que pala vai temp aparecer temp aqui cao";
$match=array();
preg_match_all('#\b(pala|cao|temp)\b#', $str, $match );
$return = array_unique( $match[0] );
print_r($return);