This question already has answers here:
PHP variable variables
(6 answers)
Closed 8 years ago.
I'm trying to create a variable and name it after the content of another variable.
For example
$newname = "x";
//dosomething to create the variable $x
They are called variable-variables:
${$newname} = 'stuff';
If you have more, consider using an array and extract variables from it:
$vars = array(...); // keys = variable name, value = variable value
extract($vars, EXTR_SKIP);
Check this :
$a = 'hello';
$$a = 'world';
echo "$a ${$a}";
echo "$a $world";
Hope to be useful.
Related
This question already has answers here:
What does "&" mean in '&$var' in PHP? [duplicate]
(2 answers)
Closed 3 months ago.
<?php
function doSomething( &$arg ){
$return = $arg;
$arg += 1;
return $return;
}
$a = 3;
$b = doSomething( $a );
echo $a.' ';
echo $b;
?>
I know the answer a=4 and b=3 I understand how b= 3 but how come value of the a increased
The & operator tells PHP not to copy the variable when passing it to the function. Instead, a reference to the variable is passed into the function, thus the function modifies the original variable instead of a copy.
Therefore $arg += 1; will increase $a
This question already has answers here:
Reference Guide: What does this symbol mean in PHP? (PHP Syntax)
(24 answers)
Closed 10 years ago.
I was trying to find this answer on Google, but I guess the symbol & works as some operator, or is just not generally a searchable term for any reason.. anyhow. I saw this code snippet while learning how to create WordPress plugins, so I just need to know what the & means when it precedes a variable that holds a class object.
//Actions and Filters
if (isset($dl_pluginSeries)) {
//Actions
add_action('wp_head', array(&$dl_pluginSeries, 'addHeaderCode'), 1);
//Filters
add_filter('the_content', array(&$dl_pluginSeries, 'addContent'));
}
This will force the variable to be passed by reference. Normally, a hard copy would be created for simple types. This can come handy for large strings (performance gain) or if you want to manipulate the variable without using the return statement, eg:
$a = 1;
function inc(&$input)
{
$input++;
}
inc($a);
echo $a; // 2
Objects will be passed by reference automatically.
If you like to handle a copy over to a function, use
clone $object;
Then, the original object is not altered, eg:
$a = new Obj;
$a->prop = 1;
$b = clone $a;
$b->prop = 2; // $a->prop remains at 1
The ampersand preceding a variable represents a reference to the original, instead of a copy or just the value.
See here: http://www.phpreferencebook.com/samples/php-pass-by-reference/
This passes something by reference instead of value.
See:
http://php.net/manual/en/language.references.php
http://php.net/manual/en/language.references.pass.php
I used it for sending a variable to a function, and have the function change the variable around. After the function is done, I don't need to return the function to the return value and set the new value to my variable.
Example
function fixString(&$str) {
$str = "World";
}
$str = "Hello";
fixString($str);
echo $str; //Outputs World;
Code without the &
function fixString($str) {
$str = "World";
return $str;
}
$str = "Hello";
$str = fixString($str);
echo $str; //Outputs World;
This question already has answers here:
PHP - concatenate or directly insert variables in string
(15 answers)
Closed 6 years ago.
I have a question about dynamic variables. (I have trouble searching because I have a hard time describing my problem)
In this example:
$x = 1;
$var = "A$x";
echo $var; //prints 'A1'
Now my question is, is there a way to combine "computation" without adding another variable?
What I want to do is:
$x = 1;
$var = "A($x+1)";
echo $var; //I want to output to be 'A2' but it gives 'A(1+1)'
I know that this works:
$var = "A".($x+1)
But this is not applicable to the program that I am doing. $var is initiated on the beginning of the program and will be used at the end waiting for any value of $x.
You need to concatenate your output.
$x = 1;
$var = "A". ($x + 1);
echo $var;
In your example the "+1" is inside the quotes and thus is a literal string.
This question already has answers here:
Reference Guide: What does this symbol mean in PHP? (PHP Syntax)
(24 answers)
Closed 6 years ago.
I know what is $var and $$var will do. But in an interview they give me a problem which contains $$$var. What is that means actually. I cant find any reference for that.
It is Variable variables. This will make you understand:
<?php
$a = 123;
$b = 'a';
$var = 'b';
echo $var; //b
echo $$var; //a
echo $$$var; //123
Simply you can understand the flow:
$var is a variable and it hold value.
$$var means the new variable that name is the value of $var.
and $$$var means the new variable that name is the value of $$var.
example:
$var = 'app';
so $$var will be $app.
and so on.
This question already has answers here:
Reference Guide: What does this symbol mean in PHP? (PHP Syntax)
(24 answers)
Closed 10 years ago.
I was trying to find this answer on Google, but I guess the symbol & works as some operator, or is just not generally a searchable term for any reason.. anyhow. I saw this code snippet while learning how to create WordPress plugins, so I just need to know what the & means when it precedes a variable that holds a class object.
//Actions and Filters
if (isset($dl_pluginSeries)) {
//Actions
add_action('wp_head', array(&$dl_pluginSeries, 'addHeaderCode'), 1);
//Filters
add_filter('the_content', array(&$dl_pluginSeries, 'addContent'));
}
This will force the variable to be passed by reference. Normally, a hard copy would be created for simple types. This can come handy for large strings (performance gain) or if you want to manipulate the variable without using the return statement, eg:
$a = 1;
function inc(&$input)
{
$input++;
}
inc($a);
echo $a; // 2
Objects will be passed by reference automatically.
If you like to handle a copy over to a function, use
clone $object;
Then, the original object is not altered, eg:
$a = new Obj;
$a->prop = 1;
$b = clone $a;
$b->prop = 2; // $a->prop remains at 1
The ampersand preceding a variable represents a reference to the original, instead of a copy or just the value.
See here: http://www.phpreferencebook.com/samples/php-pass-by-reference/
This passes something by reference instead of value.
See:
http://php.net/manual/en/language.references.php
http://php.net/manual/en/language.references.pass.php
I used it for sending a variable to a function, and have the function change the variable around. After the function is done, I don't need to return the function to the return value and set the new value to my variable.
Example
function fixString(&$str) {
$str = "World";
}
$str = "Hello";
fixString($str);
echo $str; //Outputs World;
Code without the &
function fixString($str) {
$str = "World";
return $str;
}
$str = "Hello";
$str = fixString($str);
echo $str; //Outputs World;