PHP: Access Array Value on the Fly

caillou_1532 0
Viewed 19279

In php, I often need to map a variable using an array ... but I can not seem to be able to do this in a one liner. c.f. example:

// the following results in an error:
echo array('a','b','c')[$key];

// this works, using an unnecessary variable:
$variable = array('a','b','c');
echo $variable[$key];

This is a minor problem, but it keeps bugging every once in a while ... I don't like the fact, that I use a variable for nothing ;)

coding-style arrays php
9 Answers

The technical answer is that the Grammar of the PHP language only allows subscript notation on the end of variable expressions and not expressions in general, which is how it works in most other languages. I've always viewed it as a deficiency in the language, because it is possible to have a grammar that resolves subscripts against any expression unambiguously. It could be the case, however, that they're using an inflexible parser generator or they simply don't want to break some sort of backwards compatibility.

Here are a couple more examples of invalid subscripts on valid expressions:

$x = array(1,2,3);
print ($x)[1]; //illegal, on a parenthetical expression, not a variable exp.

function ret($foo) { return $foo; }
echo ret($x)[1]; // illegal, on a call expression, not a variable exp.
John_Douthat_27740

I wouldn't bother about that extra variable, really. If you want, though, you could also remove it from memory after you've used it:

$variable = array('a','b','c');
echo $variable[$key];
unset($variable);

Or, you could write a small function:

function indexonce(&$ar, $index) {
  return $ar[$index];
}

and call this with:

$something = indexonce(array('a', 'b', 'c'), 2);

The array should be destroyed automatically now.

onnodb_10370

Or something like this, if you need the array value in a variable

$variable = array('a','b','c');
$variable = $variable[$key];
Admin1

though the fact that dereferencing has been added in PHP >=5.4 you could have done it in one line using ternary operator:

echo $var=($var=array(0,1,2,3))?$var[3]:false;

this way you don't keep the array only the variable. and you don't need extra functions to do it...If this line is used in a function it will automatically be destroyed at the end but you can also destroyed it yourself as said with unset later in the code if it is not used in a function.

user_101270600
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