This expression evaluates what follows as a regular PHP expression except that '->' are replaced by dots '.' and variable names does not need to be prefixed with a dollar '$' sign.

A dot '.' separated from the rest of expression by spaces is assumed to be a concatenation sign.

php:'string ${varReplaced}'
php:'string ${some.path().to[0].var}'
php:NOT foo OR (bar GT baz)
php:a + b
php:array('a', 'b', 'c')
php:range(0, 90)
php:foo . a.b.c(e) . htmlentities(SomeClass::staticMethod())

php: should be used with care and won't be needed in 80% of your templates but sometimes you will need to invoke some special PHP method to be certain whether a user is logged in, or to retrieve specific complex data depending on some conditions, dynamically inside the template.