I saw this code in some library
if (\count($this->variablesGlobal) > 0) {
    $this->variables = \array_merge($variables, $this->variablesGlobal);
    $variables = $this->variables;
} else {
    $this->variables = $variables;
}
and I wonder why is it has \ in php keywords.
I read the documentation about count, it simply state count and just used count in example without \
