> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# PHP Assignment
The `=` operator in PHP is the basic assignment operator. It evaluates the expression on its right-hand side (RHS) and writes the resulting value into the memory location referenced by the operand on its left-hand side (LHS).
```php theme={"dark"}
$lvalue = expression;
```
## Technical Characteristics
**L-values and R-values**
The LHS operand must be a valid l-value (a variable, array index, or object property). The RHS operand can be any valid r-value, which includes literals, variables, function return values, or complex expressions.
**Return Value**
In PHP, assignment is an expression, not just a statement. The `=` operator returns the value that was assigned to the LHS. This allows the assignment operation to be embedded within larger expressions.
```php theme={"dark"}
// The expression ($b = 5) assigns 5 to $b and evaluates to 5.
// $a is then assigned the result of 5 + 10.
$a = ($b = 5) + 10;
```
**Associativity**
The `=` operator has right-to-left associativity. When multiple assignment operators are chained, the PHP engine evaluates the rightmost assignment first and propagates the return value to the left.
```php theme={"dark"}
// Evaluated as: $x = ($y = ($z = 0));
$x = $y = $z = 0;
```
## Memory and Evaluation Behavior
The behavior of the `=` operator depends on the data type of the RHS expression:
**1. Assignment by Value (Scalars and Arrays)**
For scalar types (integers, floats, strings, booleans) and arrays, the `=` operator performs assignment *by value*. PHP creates a copy of the RHS value and assigns it to the LHS. Subsequent modifications to the LHS variable do not affect the RHS variable. *(Note: Internally, PHP optimizes array assignment using Copy-on-Write (CoW), deferring actual memory duplication until one of the variables is modified).*
```php theme={"dark"}
$a = [1, 2, 3];
$b = $a; // $b receives a copy of the array
```
**2. Object Identifier Assignment**
When the RHS is an object, the `=` operator does not copy the object itself. Instead, it copies the **object identifier**. Both the LHS and RHS variables will hold distinct copies of the identifier that point to the exact same object instance in memory.
```php theme={"dark"}
$objA = new stdClass();
$objB = $objA; // Both variables point to the same instance
```
**3. Reference Assignment (`=&`)**
To bypass standard assignment behavior and bind two variables to the exact same memory address (zval), the `=` operator must be combined with the reference operator (`&`). This creates an alias, meaning neither variable owns the value exclusively.
```php theme={"dark"}
$x = 100;
$y =& $x; // $y is now a reference to $x
```
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