Curly Brackets! {}

dougal85

Following my belated understanding of the @

I was now using the {} could somebody point me to the reference to these in the manual? As i find it hard to fully understand what exactly they are doing.

(I am trying to improve my PHP understanding)

I currently believe they make PHP process the code between the braces before the rest of the code? or something like that... I might be totally wrong.

Of course I am used to using them in if, functions, classes etc.

but Ive started to make use of them in things like

$class->{$functionname}();

and


$html = <<< ENDIT

myname is {$this->name}
blah blah blah
blah blayh blah

ENDIT;

However, why cant i do something like...


$html = <<< ENDIT

the date is {date("d/n/y")}

ENDIT;

Thanks in advance for clearing up the curly brackets/braces or whatever you like to call em 😛

do they have a technical name in PHP?

also any comments on the examples i wrote would be good, i don't know if any of them in particular are considered back or good practice?

Houdini

Actually there are a couple of uses for the curly brackets {}. Normally they are used to enclose a block of PHP code and most often these statements will be conditional statement like below:

if (condition) {
do this block of statements
like print Hello
}
else {
do this block of statements
like exit the PHP code
}

There is also the occasion where you want to print an array so here is a multidimensional array named$productPrices

$productPrices['clothing']['shirt']=20.00;
$productPrices['clothing']['pants']=25.00;
$productPrices['clothing']['dress']=40.00;

now if you wanted to print the price of a shirt in your PHP file then you can do it a couple of different ways

//no qoutes will just print 20
echo $productPrices['clothing']['shirt'];
//or with double quotes
echo "The price of a shirt is \${$productPrices['clothing']['shirt']}";
//note the use of curly braces around the variable name

dougal85

I see, but how does it work? does it process these areas first?

For example...


$test = "one";

${$test} = "hello";

echo $one;

// echo's 'hello'

Houdini

No PHP takes code line by line, the only difference is in a conditional block of code as I showed before it will go to the next line or block of code only if the condition is TRUE otherwise PHP goes through code line after line after line in the order that you write them.

dougal85

Houdini wrote:
No PHP takes code line by line,

I did mean first in the line, forgot to make that clear.

I see, so it seems that the {} is mostly just a wrapper for code 8-)

Is there something on the manual about it? i had a look but couldnt find anything that explained it. I think i understand a bit better however.

Houdini

Yes the { means the beginning of a block of code and the } means the end of a block of code regardless of the length, there are other special cases like an array variable as pointed out in my post but yes that is what it means, however a common mistake is to nest several block of conditional statements within a block and to forget to close one of those blocks and it will produce an error because there need to be a closing } curly brace (bracket) for each block. It usually look like unexpected $END in line# of your code and is usually the last or even later line of code that you worte, so you have to be careful that each block of code is closed or your code will fail.

bradgrafelman

The curly braces apply to: [man]control-structures[/man], [man]variables.variable[/man], variable parsing (esp. complex syntax), etc.

Here's an example of a variable variable name:

$foo_1 = 'Hello';
$foo_2 = ' ';
$foo_3 = 'World!';

for($i = 1; isset(${'foo_' . $i}); $i++) {
    echo ${'foo_' . $i};
} // Outputs: Hello World!

EDIT:

Houdini wrote:
a common mistake is to nest several block of conditional statements within a block and to forget to close one of those blocks

Agreed. This is why I love Notepad2 - if I click on a "(" or "{" it will automatically highlight and bold (customizable action) both the character I clicked on as well as the corresponding "}" and ")". If there isn't a matching pair, I will instantly know this by the different color it uses.