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extract (PHP 3 >= 3.0.7, PHP 4, PHP 5) extract --
Import variables into the current symbol table from an array
Descriptionint extract ( array var_array [, int extract_type [, string prefix]] )
This function is used to import variables from an array into the
current symbol table. It takes an associative array
var_array and treats keys as variable
names and values as variable values. For each key/value pair it
will create a variable in the current symbol table, subject to
extract_type and
prefix parameters.
Note:
Beginning with version 4.0.5, this function returns the number of
variables extracted.
Note:
EXTR_IF_EXISTS and EXTR_PREFIX_IF_EXISTS were introduced in version 4.2.0.
Note:
EXTR_REFS was introduced in version 4.3.0.
extract() checks each key to see whether it
has a valid variable name. It also checks for collisions with
existing variables in the symbol table. The way invalid/numeric
keys and collisions are treated is determined by the
extract_type. It can be one of the
following values:
- EXTR_OVERWRITE
If there is a collision, overwrite the existing variable.
- EXTR_SKIP
If there is a collision, don't overwrite the existing
variable.
- EXTR_PREFIX_SAME
If there is a collision, prefix the variable name with
prefix.
- EXTR_PREFIX_ALL
Prefix all variable names with
prefix. Beginning with PHP 4.0.5, this includes
numeric variables as well.
- EXTR_PREFIX_INVALID
Only prefix invalid/numeric variable names with
prefix. This flag was added in
PHP 4.0.5.
- EXTR_IF_EXISTS
Only overwrite the variable if it already exists in the
current symbol table, otherwise do nothing. This is useful
for defining a list of valid variables and then extracting
only those variables you have defined out of $_REQUEST, for
example. This flag was added in PHP 4.2.0.
- EXTR_PREFIX_IF_EXISTS
Only create prefixed variable names if the non-prefixed version
of the same variable exists in the current symbol table. This
flag was added in PHP 4.2.0.
- EXTR_REFS
Extracts variables as references. This effectively means that the
values of the imported variables are still referencing the values of
the var_array parameter. You can use this flag
on its own or combine it with any other flag by OR'ing the
extract_type. This flag was added in PHP
4.3.0.
If extract_type is not specified, it is
assumed to be EXTR_OVERWRITE.
Note that prefix is only required if
extract_type is EXTR_PREFIX_SAME,
EXTR_PREFIX_ALL, EXTR_PREFIX_INVALID
or EXTR_PREFIX_IF_EXISTS. If
the prefixed result is not a valid variable name, it is not
imported into the symbol table.
extract() returns the number of variables
successfully imported into the symbol table.
| Warning |
Do not use extract() on untrusted data, like
user-input ($_GET, ...). If you do, for example, if you want to run old
code that relies on
register_globals
temporarily, make sure you use one of the non-overwriting
extract_type values such as
EXTR_SKIP and be aware that you should extract
$_SERVER, $_SESSION,
$_COOKIE, $_POST and
$_GET in that order.
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A possible use for extract() is to import into the
symbol table variables contained in an associative array returned by
wddx_deserialize().
Example 1. extract() example |
<?php
$size = "large";
$var_array = array("color" => "blue",
"size" => "medium",
"shape" => "sphere");
extract($var_array, EXTR_PREFIX_SAME, "wddx");
echo "$color, $size, $shape, $wddx_size\n";
?>
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The above example will output: blue, large, sphere, medium |
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The $size wasn't overwritten, because we
specified EXTR_PREFIX_SAME, which resulted in
$wddx_size being created. If EXTR_SKIP was
specified, then $wddx_size wouldn't even have been created.
EXTR_OVERWRITE would have caused $size to have
value "medium", and EXTR_PREFIX_ALL would result in new variables
being named $wddx_color,
$wddx_size, and
$wddx_shape.
You must use an associative array, a numerically indexed array
will not produce results unless you use EXTR_PREFIX_ALL or
EXTR_PREFIX_INVALID.
See also compact().
User Contributed Notes
extract
kake26 at gmail dot com
30-Apr-2005 10:59
The following is a neat use for extract to store and manipulate large amounts of form data from. I basically loop through the $_POST and implode it seperating the key and value pairs by a space. Then store it in a db, the reversing function basically explodes the string to a array. Then converts the indexed array to a associative array then uses extract to seal the deal and make it easily available within a program. My main reason for sharing these are the fact I make some big web applications that store allot of forum data in a DB and these functions make it very easy to quickly and easily store and recall the data. I've contributed it because I spent many hours creating this code and recall going "I wish someone had previously submitted it to the page notes". Would have saved me allot of time and agony and I'm sure I'm not the only person that could really benefit from it, so I decided to share.
<?php
$stack = array();
foreach ($_POST as $key => $value) {
array_push($stack, $key, $value);
}
$block = implode(" ",$stack); $query = "INSERT INTO `sometable` VALUES('".$seluser."','".addslashes($block)."');";
$result = mysql_query($query) or die("Query failed for block insert: " . mysql_error());
?>
The nice thing is with the above we can quickly create a string of key and value pairs from the data the script got. Without really caring what their names are. You know how if register globals are on you say $someformvar rather than $_POST["someformvar"]; , basically the code below reads this previous created block returns it to that state. Sort of like presistant register globals.
<?php
$query = "SELECT * FROM `sometable` WHERE `blockid` = '".addslashes($bid)."';";
$result = mysql_query($query) or die("Query failed read: " . mysql_error());
$sql = mysql_fetch_array($result, MYSQL_ASSOC);
$array = eplode(" ",$sql["data"]);
for ($i = 0; $i < sizeof($array); $i+=2) {
$myassoc[$array[$i]] = isset($array[$i+1])?$array[$i+1]:NULL;
}
extract($myassoc, EXTR_OVERWRITE);
?>
pg dot perfection at gmail dot com
14-Mar-2005 04:33
Here is a little example of how an extraction method should look like when it needs to work recursive (work on nested_arrays too)...
Note that this is only an example, it can be done more easily, and more advanced too.
<?php
function extract_nested (&$array, $type = EXTR_OVERWRITE, $prefix = '')
{
if (!is_array ($array))
{
return trigger_error ('extract_nested (): First argument should be an array', E_USER_WARNING);
}
if (!empty ($prefix) && !preg_match ('#^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$#', $prefix))
{
return trigger_error ('extract_nested (): Third argument should start with a letter or an underscore', E_USER_WARNING);
}
if (($type == EXTR_PREFIX_SAME || $type == EXTR_PREFIX_ALL || $type == EXTR_PREFIX_IF_EXISTS) && empty ($prefix))
{
return trigger_error ('extract_nested (): Prefix expected to be specified', E_USER_WARNING);
}
$prefix = $prefix . '_';
foreach ($array as $key => $val)
{
if (!is_array ($array[$key]))
{
switch ($type)
{
default:
case EXTR_OVERWRITE:
$GLOBALS[$key] = $val;
break;
case EXTR_SKIP:
$GLOBALS[$key] = isset ($GLOBALS[$key]) ? $GLOBALS[$key] : $val;
break;
case EXTR_PREFIX_SAME:
if (isset ($GLOBALS[$key]))
{
$GLOBALS[$prefix . $key] = $val;
}
else
{
$GLOBALS[$key] = $val;
}
break;
case EXTR_PREFIX_ALL:
$GLOBALS[$prefix . $key] = $val;
break;
case EXTR_PREFIX_INVALID:
if (!preg_match ('#^[a-zA-Z_\x7f-\xff]$#', $key{0}))
{
$GLOBALS[$prefix . $key] = $val;
}
else
{
$GLOBALS[$key] = $val;
}
break;
case EXTR_IF_EXISTS:
if (isset ($GLOBALS[$key]))
{
$GLOBALS[$key] = $val;
}
break;
case EXTR_PREFIX_IF_EXISTS:
if (isset ($GLOBALS[$key]))
{
$GLOBALS[$prefix . $key] = $val;
}
break;
case EXTR_REFS:
$GLOBALS[$key] =& $array[$key];
break;
}
}
else
{
extract_nested ($array[$key], $type, $prefix);
}
}
}
?>
Michael Newton
02-Mar-2005 07:23
They say "If the result is not a valid variable name, it is not imported into the symbol table."
What they should say is that if _any_ of the results have invalid names, _none_ of the variables get extracted.
Under 4.3.10 on Windows 2000, I was pulling some mySQL records, but needed to convert two fields into IP addresses:
<?
extract(mysql_fetch_assoc(mysql_query('SELECT * FROM foo')));
extract(mysql_fetch_assoc(mysql_query('SELECT INET_NTOA(bar) AS bar, INET_NTOA(baz) FROM foo')));
?>
I had forgotten the second AS modifier in the SQL query. Because it couldn't extract a variable called INET_NTOA(baz) into the symbol table, it didn't do either of them.
(BTW I don't normally stack functions up like that! Just to make a short example!)
21-Feb-2005 09:31
To make this perfectly clear (hopefully), an underscore is always added when the string is prefixed.
extract(array("color" => "blue"),EXTR_PREFIX_ALL,'');// note: prefix is empty
is the same as
$color='_blue';
Aaron Stone
17-Nov-2004 12:44
If you are working porting an older application, and taking the advice above, extracting only _SERVER, _SESSING, _COOKIE, _POST, _GET, you have forgotten to extract _FILES. Putting _FILES last and using EXTR_SKIP doesn't work because the name of the file upload box is already set as a variable containing only the temporary name of the uploaded file from one of the earlier extracts (I haven't tested to see which one specifically, however). A workaround is to put _FILES last and use EXTR_OVERWRITE. This allows extract to replace that temp-name-only variable with the full array of file upload information.
Adam Monsen <adamm at wazamatta dot com>
02-Oct-2004 07:03
As shown in the example, if your 'prefix' is used, a single underscore is added to the name of the extracted variable. Meaning, a prefix of 'p' becomes a prefix of 'p_', so 'blarg' prefixed would be 'p_blarg'.
If you're not sure what variables you've created through extraction, you can call get_defined_vars() to see all defined variables in the current scope.
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