PHP Closures

Next up is something you may not use often, but 0:00 is a good thing to know, and those are closures. 0:03 Closures are anonymous functions, which are functions with no name, 0:06 that are capable of accessing variables outside of the function scope. 0:10 We'll talk more about the use of closures as call backs when we 0:14 get to the internal functions video. 0:17 For now, let's look at how this works. 0:19 Okay, to provide an example of a closure, let's start by opening and 0:24 closing a set of PHP tags. 0:27 Then inside of those, we're gonna do it a little bit differently. 0:30 Before we had used the function keyword, right? 0:33 And then added a name for our function. 0:36 In this case, we're going to use $greet as a variable, and 0:39 then set it equal to function, and then open and close parentheses. 0:44 And then open and close our curly braces, and 0:48 then follow that as a statement, enclosing it with a semi-colon. 0:51 So what this is going to do is whatever we do inside this function, it's going to set 0:55 its output to greet, $greet will contain whatever function produces. 1:01 So let's do this. 1:07 We'll add inside the function echo Hello there and then close that statement. 1:08 This way, when we call $greet then we'll get hello there. 1:13 Now let's say we have something outside of the function scope. 1:18 Well anonymous functions are not able to access things outside of 1:22 the function scope unless we utilize the use keyword. 1:26 So what we'll do here is if we have a variable named $name and that's equal 1:31 to friend and we wanna use it in our greet function, or our greet anonymous function, 1:36 then we simply say function use, and then in parentheses, $name. 1:41 This way, inside of our statement, inside of the function we can say, 1:47 echo Hello there, $name. 1:52 Notice how I've surrounded it in double quotes now so 1:54 that we can actually output the value of the string. 1:57 So to build out our example in WorkSpaces, 2:00 we are going to define our anonymous function or 2:02 our closure with $greet as the name and then we'll set that equal to a function. 2:06 And then open and close our parenthesis. 2:13 Open and close our curly braces, but 2:15 the big case here is to make sure you end this in a semicolon. 2:17 So a anonymous function is really more like 2:20 a single line function that's being assigned to a variable. 2:23 So we'll make sure we end it in a semicolon and 2:27 then inside we'll actually do an echo statement. 2:29 So we'll say echo and then our echo will be hello there, okay? 2:32 Close it with a semicolon and 2:39 then in order to call this, we'll simply type in $greet and 2:40 then open and closed parenthesis, just like we did in a variable function. 2:45 Let's head over to our preview and take a look. 2:49 Okay, so you'll see here we have hello and in there exclamation point. 2:52 So, that's exactly what we're looking for. 2:57 Okay, so let's head back over to WorkSpaces and 2:59 build out this example just a little bit more. 3:02 Let's say we wanna greet a name. 3:05 All right, so we'll say function and 3:06 then we want something outside of the function scope. 3:09 So we'll have something like name, and then we'll set that equal to Mike. 3:13 All right. 3:18 So inside of our function we want to access greet. 3:19 Well we can't just pass it through as an argument and we don't want to use global. 3:22 So we can use the keyword, use. 3:27 So we'll say use, and then what we want to use is $name. 3:30 So now we can go through and say hello and then $name. 3:35 But we want to make sure we change this to double quotes because we 3:41 are evaluating name and single quotes don't do evaluation. 3:44 So let's go ahead and hit Save and see if this does what we expect. 3:49 Refresh. 3:53 And then it says, hello Mike. 3:54 So in an anonymous function, instead of passing through an argument anonymously, 3:56 we'll just use something outside of the function scope. 4:00 So name would be outside the function scope defined on line three. 4:04 We utilize the use keyword and then pass through $name that way 4:08