型の相互変換
$name = 'Some_text';
$$name = 123;
echo $Some_text; // outputs: 123
That means practically that variable $$name
is named after a string.
add a note
User Contributed Notes変数
panosperseas at yahoo dot com (Panagiotis Gr)
26-Aug-2009 11:31
26-Aug-2009 11:31
the_good_technician [a.t.] y-a-h-o-o.
07-Aug-2009 04:32
07-Aug-2009 04:32
Sometimes it's necessary to retrieve the value of $this from within an object.
This solution dedicates a public var $ID to store a unique identifier for the object:
<?php
class Someclass {
public $ID;
public function what_is_this() {
return '$this is: ' . $this->get_varname();
}
private function get_varname() {
$this->ID = uniqid();
foreach($GLOBALS as $key => $val) {
if (is_a($val,'Someclass')) {
if ($val->ID === $this->ID) {
return $key;
break;
}
}
}
}
}
// example:
$my_var_instance = new Someclass;
echo $my_var_instance->what_is_this(); // returns '$this is: my_var_instance'
?>
mccarre at uwindsor dot canada
08-Jan-2009 08:19
08-Jan-2009 08:19
I needed a form of refelction for my work that still uses 4.2.0 that gets a variables name in context with the application.
For example
[code]class someclass{
var $field1
function getFieldsName(){
print getVarName($this->field1);
}
}
myObject = new someclass();
myObject->getFieldsName();
//This will return "myObject->field1".
[/code]
If you want to change the format you can do so with the code, my code isn't fully complete for features, but it does the basics of what is necessary for getting a variables name and it's owners.
[code]
function getVarName(&$var)
{
$old = $var; //store the value of the var so we don't lose it.
$var = "__random__" . rand() . "temp"; //assign a random string to distinguish this var from others.
//search for the random string to find the variable in $GLOBALS
//Note: this is an iterative deepening depth first search.
$key = IDDF_search(array_reverse($GLOBALS), $var); //we reverse the global array first to make it faster,
//because variables appear at the bottom of hte globals array list.
$var = $old;
return $key;
}
function IDDF_search($array, $var, $depth=100)
{
for($i=0; $i<$depth; $i++)
if($temp = RestrictedDF_search($array, $var, $i))
return $temp;
}
function RestrictedDF_search($array, $var, $depth=100, $inArray=false)
{
if($depth < 0) //we've gone to our maximum depth, so return.
return false;
$depth--;
$possibleCloseBracket = ($inArray) ? "]" : "";
foreach($array as $key => $value) {
if(is_string($value) && $value === $var)
return $key . $possibleCloseBracket;
//else
//print $key . ": the value != " . $var . "<br />";
if(is_array($value))
if($temp = RestrictedDF_search($value, $var, $depth, true))
return $key . $possibleCloseBracket . "[" . $temp;
//PHP 4.2.0 =)
if(is_object($value))
if($temp = RestrictedDF_search(get_object_vars($value), $var, $depth))
return $key . $possibleCloseBracket . "->" . $temp;
}
return false;
}
[/code]
This was built of a function noted here at an earlier date. I think he actually named his function getVarName. Mine takes it a step further combining the recursive search defined in the array_search notes as well, so a user can get the name of a variable no matter where it is in GLOBALS.
If only I had php 5 to work with at work. =P
Anonymous
20-Jul-2008 01:25
20-Jul-2008 01:25
[EDIT by danbrown AT php DOT net: The function provided by this author will give you all defined variables at runtime. It was originally written by (john DOT t DOT gold AT gmail DOT com), but contained some errors that were corrected in subsequent posts by (ned AT wgtech DOT com) and (taliesin AT gmail DOT com).]
<?php
echo '<table border=1><tr> <th>variable</th> <th>value</th> </tr>';
foreach( get_defined_vars() as $key => $value)
{
if (is_array ($value) )
{
echo '<tr><td>$'.$key .'</td><td>';
if ( sizeof($value)>0 )
{
echo '"<table border=1><tr> <th>key</th> <th>value</th> </tr>';
foreach ($value as $skey => $svalue)
{
echo '<tr><td>[' . $skey .']</td><td>"'. $svalue .'"</td></tr>';
}
echo '</table>"';
}
else
{
echo 'EMPTY';
}
echo '</td></tr>';
}
else
{
echo '<tr><td>$' . $key .'</td><td>"'. $value .'"</td></tr>';
}
}
echo '</table>';
?>
alexandre at nospam dot gaigalas dot net
07-Jul-2007 04:13
07-Jul-2007 04:13
Here's a simple solution for retrieving the variable name, based on the lucas (http://www.php.net/manual/en/language.variables.php#49997) solution, but shorter, just two lines =)
<?php
function var_name(&$var, $scope=0)
{
$old = $var;
if (($key = array_search($var = 'unique'.rand().'value', !$scope ? $GLOBALS : $scope)) && $var = $old) return $key;
}
?>
jsb17 at cornell dot edu
20-Feb-2007 04:48
20-Feb-2007 04:48
As an addendum to David's 10-Nov-2005 posting, remember that curly braces literally mean "evaluate what's inside the curly braces" so, you can squeeze the variable variable creation into one line, like this:
<?php
${"title_default_" . $title} = "selected";
?>
and then, for example:
<?php
$title_select = <<<END
<select name="title">
<option>Select</option>
<option $title_default_Mr value="Mr">Mr</option>
<option $title_default_Ms value="Ms">Ms</option>
<option $title_default_Mrs value="Mrs">Mrs</option>
<option $title_default_Dr value="Dr">Dr</option>
</select>
END;
?>
code at slater dot fr
25-Jan-2007 10:10
25-Jan-2007 10:10
Here's a pair of functions to encode/decode any string to be a valid php and javascript variable name.
<?php
function label_encode($txt) {
// add Z to the begining to avoid that the resulting
// label is a javascript keyword or it starts with a
// number
$txt = 'Z'.$txt;
// encode as urlencoded data
$txt = rawurlencode($txt);
// replace illegal characters
$illegal = array('%', '-', '.');
$ok = array('é', 'è', 'à');
$txt = str_replace($illegal,$ok, $txt);
return $txt;
}
function label_decode($txt) {
// replace illegal characters
$illegal = array('%', '-', '.');
$ok = array('é', 'è', 'à');
$txt = str_replace($ok, $illegal, $txt);
// unencode
$txt = rawurldecode($txt);
// remove the leading Z and return
return substr($txt,1);
}
?>
molnaromatic at gmail dot com
20-May-2006 12:44
20-May-2006 12:44
Simple sample and variables and html "templates":
The PHP code:
variables.php:
<?php
$SYSN["title"] = "This is Magic!";
$SYSN["HEADLINE"] = "Ez magyarul van"; // This is hungarian
$SYSN["FEAR"] = "Bell in my heart";
?>
index.php:
<?php
include("variables.php");
include("template.html");
?>
The template:
template.html
<html>
<head><title><?=$SYSN["title"]?></title></head>
<body>
<H1><?=$SYSN["HEADLINE"]?></H1>
<p><?=$SYSN["FEAR"]?></p>
</body>
</html>
This is simple, quick and very flexibile
Mike at ImmortalSoFar dot com
25-Nov-2005 10:03
25-Nov-2005 10:03
References and "return" can be flakey:
<?php
// This only returns a copy, despite the dereferencing in the function definition
function &GetLogin ()
{
return $_SESSION['Login'];
}
// This gives a syntax error
function &GetLogin ()
{
return &$_SESSION['Login'];
}
// This works
function &GetLogin ()
{
$ret = &$_SESSION['Login'];
return $ret;
}
?>
david at removethisbit dot futuresbright dot com
10-Nov-2005 09:25
10-Nov-2005 09:25
When using variable variables this is invalid:
<?php
$my_variable_{$type}_name = true;
?>
to get around this do something like:
<?php
$n="my_variable_{$type}_name";
${$n} = true;
?>
(or $$n - I tend to use curly brackets out of habit as it helps t reduce bugs ...)
Chris Hester
31-Aug-2005 12:09
31-Aug-2005 12:09
Variables can also be assigned together.
<?php
$a = $b = $c = 1;
echo $a.$b.$c;
?>
This outputs 111.
Mike Fotes
09-Jul-2005 06:46
09-Jul-2005 06:46
In conditional assignment of variables, be careful because the strings may take over the value of the variable if you do something like this:
<?php
$condition = true;
// Outputs " <-- That should say test"
echo "test" . ($condition) ? " <-- That should say test" : "";
?>
You will need to enclose the conditional statement and assignments in parenthesis to have it work correctly:
<?php
$condition = true;
// Outputs "test <-- That should say test"
echo "test" . (($condition) ? " <-- That should say test " : "");
?>
josh at PraxisStudios dot com
17-May-2005 08:06
17-May-2005 08:06
As with echo, you can define a variable like this:
<?php
$text = <<<END
<table>
<tr>
<td>
$outputdata
</td>
</tr>
</table>
END;
?>
The closing END; must be on a line by itself (no whitespace).
[EDIT by danbrown AT php DOT net: This note illustrates HEREDOC syntax. For more information on this and similar features, please read the "Strings" section of the manual here: http://www.php.net/manual/en/language.types.string.php ]
mike at go dot online dot pt
07-Apr-2005 04:18
07-Apr-2005 04:18
In addition to what jospape at hotmail dot com and ringo78 at xs4all dot nl wrote, here's the sintax for arrays:
<?php
//considering 2 arrays
$foo1 = array ("a", "b", "c");
$foo2 = array ("d", "e", "f");
//and 2 variables that hold integers
$num = 1;
$cell = 2;
echo ${foo.$num}[$cell]; // outputs "c"
$num = 2;
$cell = 0;
echo ${foo.$num}[$cell]; // outputs "d"
?>
lucas dot karisny at linuxmail dot org
15-Feb-2005 12:42
15-Feb-2005 12:42
Here's a function to get the name of a given variable. Explanation and examples below.
<?php
function vname(&$var, $scope=false, $prefix='unique', $suffix='value')
{
if($scope) $vals = $scope;
else $vals = $GLOBALS;
$old = $var;
$var = $new = $prefix.rand().$suffix;
$vname = FALSE;
foreach($vals as $key => $val) {
if($val === $new) $vname = $key;
}
$var = $old;
return $vname;
}
?>
Explanation:
The problem with figuring out what value is what key in that variables scope is that several variables might have the same value. To remedy this, the variable is passed by reference and its value is then modified to a random value to make sure there will be a unique match. Then we loop through the scope the variable is contained in and when there is a match of our modified value, we can grab the correct key.
Examples:
1. Use of a variable contained in the global scope (default):
<?php
$my_global_variable = "My global string.";
echo vname($my_global_variable); // Outputs: my_global_variable
?>
2. Use of a local variable:
<?php
function my_local_func()
{
$my_local_variable = "My local string.";
return vname($my_local_variable, get_defined_vars());
}
echo my_local_func(); // Outputs: my_local_variable
?>
3. Use of an object property:
<?php
class myclass
{
public function __constructor()
{
$this->my_object_property = "My object property string.";
}
}
$obj = new myclass;
echo vname($obj->my_object_property, $obj); // Outputs: my_object_property
?>
jospape at hotmail dot com
05-Feb-2005 07:45
05-Feb-2005 07:45
<?php
$id = 2;
$cube_2 = "Test";
echo ${cube_.$id};
// will output: Test
?>
ringo78 at xs4all dot nl
14-Jan-2005 08:27
14-Jan-2005 08:27
<?php
// I am beginning to like curly braces.
// I hope this helps for you work with them
$filename0="k";
$filename1="kl";
$filename2="klm";
$i=0;
for ($varname = sprintf("filename%d",$i); isset ( ${$varname} ) ; $varname = sprintf("filename%d", $i) ) {
echo "${$varname} <br>";
$varname = sprintf("filename%d",$i);
$i++;
}
?>
Carel Solomon
07-Jan-2005 11:02
07-Jan-2005 11:02
You can also construct a variable name by concatenating two different variables, such as:
<?php
$arg = "foo";
$val = "bar";
//${$arg$val} = "in valid"; // Invalid
${$arg . $val} = "working";
echo $foobar; // "working";
//echo $arg$val; // Invalid
//echo ${$arg$val}; // Invalid
echo ${$arg . $val}; // "working"
?>
Carel
raja shahed at christine nothdurfter dot com
25-May-2004 05:58
25-May-2004 05:58
<?php
error_reporting(E_ALL);
$name = "Christine_Nothdurfter";
// not Christine Nothdurfter
// you are not allowed to leave a space inside a variable name ;)
$$name = "'s students of Tyrolean language ";
print " $name{$$name}<br>";
print "$name$Christine_Nothdurfter";
// same
?>
webmaster at daersys dot net
20-Jan-2004 04:15
20-Jan-2004 04:15
You don't necessarily have to escape the dollar-sign before a variable if you want to output its name.
You can use single quotes instead of double quotes, too.
For instance:
<?php
$var = "test";
echo "$var"; // Will output the string "test"
echo "\$var"; // Will output the string "$var"
echo '$var'; // Will do the exact same thing as the previous line
?>
Why?
Well, the reason for this is that the PHP Parser will not attempt to parse strings encapsulated in single quotes (as opposed to strings within double quotes) and therefore outputs exactly what it's being fed with :)
To output the value of a variable within a single-quote-encapsulated string you'll have to use something along the lines of the following code:
<?php
$var = 'test';
/*
Using single quotes here seeing as I don't need the parser to actually parse the content of this variable but merely treat it as an ordinary string
*/
echo '$var = "' . $var . '"';
/*
Will output:
$var = "test"
*/
?>
HTH
- Daerion
unleaded at nospam dot unleadedonline dot net
15-Jan-2003 02:37
15-Jan-2003 02:37
References are great if you want to point to a variable which you don't quite know the value yet ;)
eg:
<?php
$error_msg = &$messages['login_error']; // Create a reference
$messages['login_error'] = 'test'; // Then later on set the referenced value
echo $error_msg; // echo the 'referenced value'
?>
The output will be:
test