$re = '`.*\bis:(Foo|Bar)\b.*`m';
$str = '"is:Baz is:Foo FooBar" # Captures "Foo"
"is:Foo FooBar is:Bar" # Captures "Bar"
"is:Bar FooBar FooBaz Baz" # Captures "Bar"
"FooBar is:Bar FooBaz" # Captures "Bar"
"FooBar is:Xyzzy is:Foo" # Captures "Foo
"is:Baz FooBar is:Foo" # Captures "Foo"
"FooBar is:Foo is:Xyzzy" # No capture';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php