Function syntax error in PHP

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();
 }

• Qirel: getSomething() { /* Do stuff here */ }
• Funk Forty Niner: that requires a class to run with, seeing "public".
• Carlos Gomez: I know that guys, but a external library have this sintaxis. See the edit

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() {}

• ceejayoz: And if it's an external library, you'll need to use an older PHP5-compatible version of it.

Answer 2

You are using the shorthand if/else syntax of PHP here, but let's use the long way:

public function getProxiesTargetDir()
{
 if( $this->proxiesTargetDir == false ){
 return ( $this->proxiesTargetDir = sys_get_temp_dir() );
 }
 else{ 
 return $this->proxiesTargetDir;
 }
}

If have also deleted the :string, because it can make errors and it is not really necessary here.