Initializing Multiple PHP Variables Simultaneously

Question

How may I initialize multiple PHP variables with a value of zero simultaneously without using an array? I wish to write code that is essentially equivalent to the following:

$first = 0;
$second = 0;
$third = 0;
$fourth = 0;

Possible duplicate of [Assign same value to multiple variables](http://stackoverflow.com/questions/11651594/assign-same-value-to-multiple-variables) — Anderson Green, Aug 27 '16 at 00:56

score 132 · Accepted Answer · answered Mar 11 '12 at 02:01

132

$first = $second = $third = $fourth = 0;

answered Mar 11 '12 at 02:01

rid

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Doesn't this run into the problem that when you change $fourth, you also change the rest? – Alec Jul 28 '16 at 08:09
11

If you change `$fourth`, you won't change the rest, because `0` is a value, not a reference. If you would have done something like `$fourth = 0; $third = &$fourth; $second = &$fourth; $first = &$fourth`, then all the other variables would be references to `$fourth` (not the value `0`), and changing `$fourth` would be reflected in the other variables as well. – rid Jul 28 '16 at 17:14
14

This multiple assignment works because, in PHP, assignment is an expression which returns the assigned value. Thus, `$fourth = 0` is an expression which returns the value `0`. This value is then assigned to `$third`, and, since this assignment is also an expression, the return value of assigning `0` to `$third` is again the value `0`, etc. – rid Jul 28 '16 at 17:17

slevy1 · Answer 2 · 2017-06-04T19:12:22.357

While it is feasible to initialize multiple variables using a comma operator within a for-loop, as follows:

<?php
for ($a=0,$b=0,$c=0,$d=0;;) {
    break;
}
var_dump($a,$b,$c,$d);

(See demo here)

the list construct provides a more efficient way to perform multiple variable assignment, as depicted in the following example:

<?php

list( $first, $second, $third, $fourth ) = array( 0, 0, 0, 0 );
var_dump($first, $second, $third, $fourth );

See demo here

One may wish to reconsider avoiding the usage of arrays to achieve multiple initialized variables. With PHP7.1+ one may write simpler, robust code if one utilizes array destructuring available with short array syntax, as follows:

<?php

[$first, $second, $third, $fourth ] = [0, 0, 0, 0];
var_dump($first, $second, $third, $fourth );

See demo here.

If one needs to be certain that the variables being initialized were not previously set, see this related discussion, particularly this response.

You can use this method for declaring multiple variables with different values, and that makes this far more useful. — Alec, Jul 28 '16 at 08:09
@Alec This is a bit confusing for declaring variables with different values. — Dávid Horváth, Dec 09 '17 at 08:12

score 2 · Answer 3 · answered Sep 30 '19 at 13:25

If you want to initialize multiple array variables then use

# Initialize multiple array variables with Empty values
$array_1 = $array_2 = $array_3 = array();

# Initialize multiple array variables with Some values in it
list( $array_1, $array_2, $array_3) = array('one','two','three');

# Print value of array variables
var_dump($array_1,$array_2,$array_3);

Output:
*******
string 'one' (length=3)
string 'two' (length=3)
string 'three' (length=5)

If you want to initialize multiple regular variables then use

# Initialize multiple regular variables with values
$a = $b = $c = 'Hello PHP';
echo $a.'<br>',$b.'<br>', $c.'<br>';

Output:
*******
Hello PHP
Hello PHP
Hello PHP

Initializing Multiple PHP Variables Simultaneously

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