PHP中的函数语法错误

Question

Does anyone know this PHP function syntax and how it works? It's not working with PHP 5.5

    public function getProxiesTargetDir() : string
    {
        return $this->proxiesTargetDir ?: $this->proxiesTargetDir = sys_get_temp_dir();
    }

Answer 1

You are using typed returns public function getProxiesTargetDir() : string which only exists starting from PHP 7.

For previous versions just remove : string > public function getProxiesTargetDir() {}