compact

(PHP 4, PHP 5, PHP 7, PHP 8)

compactCreate array containing variables and their values

Description

compact(array|string $var_name, array|string ...$var_names): array

Creates an array containing variables and their values.

For each of these, compact() looks for a variable with that name in the current symbol table and adds it to the output array such that the variable name becomes the key and the contents of the variable become the value for that key. In short, it does the opposite of extract().

Note:

Before PHP 7.3, any strings that are not set will silently be skipped.

Parameters

var_name
var_names

compact() takes a variable number of parameters. Each parameter can be either a string containing the name of the variable, or an array of variable names. The array can contain other arrays of variable names inside it; compact() handles it recursively.

Return Values

Returns the output array with all the variables added to it.

Errors/Exceptions

compact() issues an E_WARNING level error if a given string refers to an unset variable.

Changelog

Version Description
8.0.0 If a given string references an unset variable, an E_WARNING level error is now issued.
7.3.0 compact() now issues an E_NOTICE level error if a given string refers to an unset variable. Formerly, such strings have been silently skipped.

Examples

Example #1 compact() example

<?php
$city
= "San Francisco";
$state = "CA";
$event = "SIGGRAPH";

$location_vars = array("city", "state");

$result = compact("event", $location_vars);
print_r($result);
?>

The above example will output:

Array
(
    [event] => SIGGRAPH
    [city] => San Francisco
    [state] => CA
)

Notes

Note: Gotcha

Because variable variables may not be used with PHP's Superglobal arrays within functions, the Superglobal arrays may not be passed into compact().

See Also

  • extract() - Import variables into the current symbol table from an array

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User Contributed Notes 5 notes

up
170
M Spreij
17 years ago
Can also handy for debugging, to quickly show a bunch of variables and their values:

<?php
print_r
(compact(explode(' ', 'count acw cols coldepth')));
?>

gives

Array
(
[count] => 70
[acw] => 9
[cols] => 7
[coldepth] => 10
)
up
63
lekiagospel at gmail dot com
4 years ago
Consider these two examples. The first as used in the manual, and the second a slight variation of it.

Example #1

<?php
$city
= "San Francisco";
$state = "CA";
$event = "SIGGRAPH";

$location_vars = array("city", "state");

$result = compact("event", $location_vars);
print_r($result);
?>

Example #1 above will output:

Array
(
[event] => SIGGRAPH
[city] => San Francisco
[state] => CA
)

Example #2

<?php
$city
= "San Francisco";
$state = "CA";
$event = "SIGGRAPH";

$location_vars = array("city", "state");

$result = compact("event", "location_vars");
print_r($result);
?>

Example #2 above will output:

Array
(
[event] => SIGGRAPH

[location_vars] => Array
(
[0] => city
[1] => state
)

)

In the first example, the value of the variable $location_values (which is an array containing city, and state) is passed to compact().

In the second example, the name of the variable $location_vars (i.e without the '$' sign) is passed to compact() as a string. I hope this further clarifies the points made in the manual?
up
56
jmarkmurph at yahoo dot com
8 years ago
So compact('var1', 'var2') is the same as saying array('var1' => $var1, 'var2' => $var2) as long as $var1 and $var2 are set.
up
2
c dot smith at fantasticmedia dot co dot uk
9 months ago
If you must utilise this knowing that a variable may be unset, then you need to use an alternative method.

So instead of the following:

<?php
$var1
= "lorem";
$var2 = "ipsum";
$result = compact('var1', 'var2', 'unsetvar');
?>

Consider the following:

<?php
$var1
= "lorem";
$var2 = "ipsum";
$result = [];
foreach( [
'var1', 'var2', 'unsetvar'] as $attr ) {
if ( isset( $
$attr ) ) {
$result[ $attr ] = $$attr;
}
}
?>
up
28
Robc
13 years ago
The description says that compact is the opposite of extract() but it is important to understand that it does not completely reverse extract(). In particluar compact() does not unset() the argument variables given to it (and that extract() may have created). If you want the individual variables to be unset after they are combined into an array then you have to do that yourself.
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