PHP : Function Reference : Array Functions : extract PHP Examples Tutorials References

Example 305. extract() example

<?php

/* Suppose that $var_array is an array returned from

   wddx_deserialize */

$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";

?>

The above example will output:

copy to clipboard

blue, large, sphere, medium

Related Examples ( Source code ) » extract

Code Examples / Notes » extract

This function provides exactly the same functionality as extract except that a parameter was added defining the extract target. This function can be used if your PHP installation does not support the required Flags or more important if you would like to extract arrays to another destination as to $GLOBALS, i.e. other arrays or objects. The only difference to extract is that extract_to moves the array pointer of $arr to the end as $arr is passed by reference to support the EXTR_REFS flag. <?php if( !defined('EXTR_PREFIX_ALL') ) define('EXTR_PREFIX_ALL', 3); if( !defined('EXTR_PREFIX_INVALID') ) define('EXTR_PREFIX_INVALID', 4); if( !defined('EXTR_IF_EXISTS') ) define('EXTR_IF_EXISTS', 5); if( !defined('EXTR_PREFIX_IF_EXISTS') ) define('EXTR_PREFIX_IF_EXISTS', 6); if( !defined('EXTR_REFS') ) define('EXTR_REFS', 256); function extract_to( &$arr, &$to, $type=EXTR_OVERWRITE, $prefix=false ){ if( !is_array( $arr ) ) return trigger_error("extract_to(): First argument should be an array", E_USER_WARNING ); if( is_array( $to ) ) $t=0; else if( is_object( $to ) ) $t=1; else return trigger_error("extract_to(): Second argument should be an array or object", E_USER_WARNING ); if( $type==EXTR_PREFIX_SAME || $type==EXTR_PREFIX_ALL || $type==EXTR_PREFIX_INVALID || $type==EXTR_PREFIX_IF_EXISTS ) if( $prefix===false ) return trigger_error("extract_to(): Prefix expected to be specified", E_USER_WARNING ); else $prefix .= '_'; $i=0; foreach( $arr as $key=>$val ){ $nkey = $key; $isset = $t==1 ? isset( $to[$key] ) : isset( $to->$key ); if( ( $type==EXTR_SKIP && $isset ) || ( $type==EXTR_IF_EXISTS && !$isset ) ) continue; else if( ( $type==EXTR_PREFIX_SAME && $isset ) || ( $type==EXTR_PREFIX_ALL ) || ( $type==EXTR_PREFIX_INVALID && !preg_match( '#^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$#', $key ) ) ) $nkey = $prefix.$key; else if( $type==EXTR_PREFIX_IF_EXISTS ) if( $isset ) $nkey = $prefix.$key; else continue; if( !preg_match( '#^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$#', $nkey ) ) continue; if( $t==1 ) if( $type & EXTR_REFS ) $to->$nkey = &$arr[$key]; else $to->$nkey = $val; else if( $type & EXTR_REFS ) $to[$nkey] = &$arr[$key]; else $to[$nkey] = $val; $i++; } return $i; } // e.g.: extract_to( $myarray, $myobject, EXTR_IF_EXISTS ); ?>

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!)

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); } // store it $block = implode(" ",$stack); // yeilds a space delimited string // insert query to store string in DB here, like the one below $query = "INSERT INTO `sometable` VALUES('".$seluser."','".addslashes($block)."');"; $result = mysql_query($query) or die("Query failed for block insert: " . mysql_error()); // note $seluser in my case is a user ID associated with that block // in one of my web apps ?> 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 // insert query to grab the previously stored string here $query = "SELECT * FROM `sometable` WHERE `blockid` = '".addslashes($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); // now you're key and value pairs from $_POST have been restored // instead of $_POST ?>

Sometimes you may want to extract only a named subset of the key/value pairs in an array. This keeps things more orderly and could prevent an unrelated variable from getting clobbered from an errant key. For example, $things = 'unsaid'; $REQUEST = array(He=>This, said=>1, my=>is, info=>2, had=>a, very=>3, important=>test, things=>4); $aVarToExtract = array(my, important, info); extract (array_intersect_key ($REQUEST, array_flip($aVarToExtract))); will extract $my = 'is'; $important = 'test'; $info = 2; but will leave certain $things = 'unsaid' Csaba Gabor from Vienna NB. Of course the composite request coming in from a web page is in $_REQUEST.

It's really easy to open gaping security holes using extract() on $_REQUEST, $_GET, etc. You have to be really sure of what you're doing, and use the proper flags on extract() to avoid clobbering important variables. For instance, the submission by kake26 at gmail dot com will not only perfectly emulate register globals (that's bad), but it'll store it in a database and recall the same variables every time the script runs (essentially allowing an attacker to attack your script every time it runs via one attack). Oops! To fix it, you'd have to get creative with flags. Maybe you could use EXTR_PREFIX_ALL instead of EXTR_OVERWRITE, for example. Of course, you should also sanitize the form elements to ensure there's no php code in them, and also to make sure any very important variables aren't in the form data. (like the classic $is_admin = true attack)

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.

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 /** * A nested version of the extract () function. * * @param array $array The array which to extract the variables from * @param int $type The type to use to overwrite (follows the same as extract () on PHP 5.0.3 * @param string $prefix The prefix to be used for a variable when necessary */ function extract_nested (&$array, $type = EXTR_OVERWRITE, $prefix = '') { /** * Is the array really an array? */ if (!is_array ($array)) { return trigger_error ('extract_nested (): First argument should be an array', E_USER_WARNING); } /** * If the prefix is set, check if the prefix matches an acceptable regex pattern * (the one used for variables) */ if (!empty ($prefix) && !preg_match ('#^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$#', $prefix)) { return trigger_error ('extract_nested (): Third argument should start with a letter or an underscore', E_USER_WARNING); } /** * Check if a prefix is necessary. If so and it is empty return an error. */ if (($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); } /** * Make sure the prefix is oke */ $prefix = $prefix . '_'; /** * Loop thru the array */ foreach ($array as $key => $val) { /** * If the key isn't an array extract it as we need to do */ if (!is_array ($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; } } /** * The key is an array... use the function on that index */ else { extract_nested ($array[$key], $type, $prefix); } } } ?>

Following up on ktwombley at gmail dot com's post: Presumably one easy way of dealing with this security issue is to use the EXTR_IF_EXISTS flag and make sure a) your define acceptable input variables beforehand (i.e. as empty variables) b) Sanitise any user input to avoid unacceptable variable content. If you do these two things, then I'm not sure I see the difference between extract($_REQUEST,EXTR_IF_EXISTS); and assigning each of the variables by hand. I'm not talking here about the idea of storing the variables in a database, just the immediately necessary steps to allow you to use extract on REQUEST arrays with relative safety.

adam monsen

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.

owk dot ch199_ph

And if you want with PHP 5 an easy way to extract $V by reference, try this : <?php foreach ($V as $k => &$v) { $$k =& $v; } ?> It can be used to create special kind of "free args" functions that let you choose when you call them the way you send variables, and which ones. They are moreover very fast to call thanks to references : <?php function free_args (&$V) { foreach ($V as $k => &$v) { $$k =& $v; } unset ($k); unset ($v); unset ($V); // be careful that if you need to extract $k, $v or $V variables you should find other names for them in the lines above (ie. $__k, $__v and $__V) } $huge_text = '...'; $a = array ('arg1' => 'val1', 'arg2' => &$huge_text); // in this call, only $arg2 will be a true reference in the function free_args ($a); ?> Be warned that you can't write : "<?php free_args (array ('arg1' => 'val1')); ?>" because the array can't be referenced by the function, as it's not yet created when the function starts.

anon

A warning about extract() and null values. This might be an actual Zend2 Engine bug, but it's bad programming practice, so I'm sharing it here instead. I often work in envrionments where E_STRICT (which would prevent errors like this) isn't on, and I don't have access to change it. I also use a very simple template class that in a nutshell works like this: $t = new Template('somefile.php'); $t->title = $title; $t->body = $body; $t->display(); display() more or less looks like this: function display(){ extract(get_object_vars($this),EXTR_REFS); ob_start(); include $this->templateFileName; return ob_get_clean(); } If any of the assigned values are null (let's say that in this case $title wasn't initialized above) it causes the engine to do all sorts of incredibly whacky stuff like certifiably lose track of variables in an incredibly inconsistent way. I traced the problem down to the fact that it's using the EXTR_REFS flag. I assume that in PHP's internal variable storage or reference counting mechanism, that trying to extract null references makes it lose track or count of something or rather. In a nutshell, if you start getting wierd behavior when using extract() make sure that the array or object you are trying to get variables out of doesn't contain null keys or values!

extract

Import variables into the current symbol table from an array (PHP 4, PHP 5)
int extract ( array var_array [, int extract_type [, string prefix]] )

Example 305. extract() example

Related Examples ( Source code ) » extract

Code Examples / Notes » extract

Change Language

extract

Import variables into the current symbol table from an array (PHP 4, PHP 5) int extract ( array var_array [, int extract_type [, string prefix]] )

Example 305. extract() example

Related Examples ( Source code ) » extract

Code Examples / Notes » extract

Change Language

Import variables into the current symbol table from an array (PHP 4, PHP 5)
int extract ( array var_array [, int extract_type [, string prefix]] )