How to declare multiple variables in PHP? (Introduction to multiple methods)

When we write PHP-related program code, declaring variables is a basic operation. So this article will introduce how to declare variables in PHP. Hope it helps friends in need.

First of all, everyone needs to understand what is a php variable? That is, variables in PHP are containers used to store information, similar to sets in mathematics. The assignment method is similar to algebra in mathematics. For example: a=1;b=2; then c=a b;c=3.

Note: Throughout PHP programming, these letters represent variables.

1. Set ordinary variables $a = "hi";

2. Static variables

static $a = 0 inside the function;

Note : Assigning the result of an expression in the declaration will cause parsing errors such as static $a =3 3; (error)

Static variables only exist in the local function domain (inside the function), after the function is executed , the variable value will not be lost and can be used for recursive calls

3. Assign a value to the variable:

$bar = &$foo;

Add the ampersand to the Before the assigned variable

Changing the new variable will affect the original variable. This assignment operation is faster

Note: Only named variables can be assigned addresses

$bar = &$a;
$bar = &$foo;

Changing the value of $bar can only change the value of variable foo, but not the value of a (the reference has changed)

4. Variable variables (symbol ($))

$$a = "world";

Both variables are defined: the contents of

$a is "hello" and the content of $hello is "world".

Therefore, it can be expressed as:

echo "$a ${$a}"; or echo "$a $hello"; they will both output: hello world

To use mutable variables with arrays, an ambiguity must be resolved. This is what the parser needs to know when writing $$a[1] that you want $a[1] As a variable, you still want to use $$a as a variable and take out the value with index [1] in the variable. The syntax to solve this problem is to use ${$a[1]}, use ${$a}[1] for the second case.

#The above is an introduction to the relevant knowledge about how to declare variables in PHP. I hope it will be helpful to friends in need. If there are any shortcomings, I hope the netizens can give me suggestions.

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