PHP Forum

**jim.thornton** · 11-04-2005, 01:47 AM

I am trying to teach myself PHP. I have been using SAMS Teach yourself PHP, MySQL & Apache in 24 hours.

I don't understand one of the examples used and was hoping for some clarification.

Code:

1: <html>
 2: <head>
 3: <title>Listing 6.14</title>
 4: </head>
 5: <body>
 6: <?php
 7:
 8: function tagWrap($tag, $txt, $func = "") {
 9:     if ((!empty($txt)) && (function_exists($func))) {
10:         $txt = $func($txt);
11:         return "<$tag>$txt</$tag>\n";
12:     }
13: }
14:
15: function underline($txt) {
16:     return "<u>$txt</u>";
17: }
18:
19: echo tagWrap('b', 'make me bold');
20: // will print <b>make me bold</b>
21:
22: echo tagWrap('i', 'underline me too', "underline");
23: // will print <i><u>underline me too</u></i>
24:
25: echo tagWrap('i', 'make me italic and quote me',
26:     create_function('$txt', 'return "&quot;$txt&quot;";'));
27: // will print <i>&quot;make me italic and quote me&quot;</i>
28: ?>
29: </body>
30: </html>

I don't understand this:

Quote:

Finally, on line 25, we call tagWrap(), which wraps text in quotation entities. Of course, it would be quicker to simply add the entities to the text to be transformed ourselves, but this illustrates the point that function_exists() works as well on anonymous functions as it does on strings representing function names.

I don't understand where function_create is coming from and how it works in this snipet of code.

Can anyone please clarify?

Zinc.

**0beron** · 11-04-2005, 04:47 AM

create_function is a builtin PHP function - there is documentation for it here:
http://www.php.net/manual/en/functio...e-function.php

echo tagWrap('i', 'underline me too', "underline"); means 'call the function called underline on the text, then put <i> tags round it'

echo tagWrap('i', 'make me italic and quote me',
create_function('$txt', 'return ""$txt"";'));
means 'call this function I've just given you on the text and then put <i> tags round it'
It is an anonymous function since it is never given a name, it gets created inside the arguments to tagWrap() and fed straight in.

**jim.thornton** · 11-04-2005, 10:53 AM

thanks... I now understand it. However, I still don't see why someone would want to do this rather than just putting the code inside the function. Could you enlighten me?

Zinc.

**0beron** · 11-04-2005, 03:31 PM

Say you want a function that returns another function, but what this new function does depends on results from some other part of your code. You can't know what these results will be before you start, so create_function allows you to create new bits of PHP using PHP itself.

Anonymous functions are useful when you need to pass a function as an argument, but only want to use it once. This way you don't have to store them or come up with new names for them all. Of course if you want to refer tothem again you have to assign them to a variable.

**jim.thornton** · 11-06-2005, 04:24 PM

Thanks.