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# PHP Do-While Loop
A `do-while` loop is a post-test control flow structure that guarantees the execution of its code block at least once. Unlike a standard `while` loop, which evaluates its condition prior to execution, the `do-while` loop evaluates the boolean condition at the end of the iteration.
## Syntax
```php theme={"dark"}
do {
// Statements to execute
} while (condition);
```
If the loop body consists of only a single statement, the curly braces `{}` are optional. Variables must be initialized prior to use to avoid undefined variable warnings in modern PHP:
```php theme={"dark"}
$i = 0;
do $i++; while ($i < 5);
```
## Execution Flow
1. **Execution:** The PHP interpreter enters the `do` block and executes the enclosed statements sequentially.
2. **Evaluation:** Upon reaching the `while` clause, the `condition` expression is evaluated in a boolean context.
3. **Iteration or Termination:**
* If the condition evaluates to `true`, the execution pointer jumps back to the beginning of the `do` block.
* If the condition evaluates to `false`, the loop terminates, and control passes to the next sequential statement in the script.
## Technical Characteristics
* **Trailing Semicolon:** The `while (condition)` statement at the end of the loop must be explicitly terminated with a semicolon (`;`). Omitting this will result in a parse error.
* **Guaranteed Initial Execution:** Because the condition is evaluated at the bottom of the loop, the code block will always execute the first time, even if the condition is inherently `false` at the start of the execution cycle.
* **Scope:** PHP lacks block-level scope for variables. Variables declared or initialized inside the `do` block are fully accessible within the `while` condition and in the surrounding global or function scope following the loop.
* **Syntax Constraints:** Unlike the standard `while` loop, which supports an alternative syntax for templating (`while (...): ... endwhile;`), the `do-while` loop does not support an alternative syntax.
* **Control Statements:**
* `break`: Immediately terminates the loop and transfers control to the statement following the loop.
* `continue`: Skips the remaining statements in the current iteration and immediately jumps to the `while` condition evaluation to determine if the next iteration should begin.
## Code Example
The following example demonstrates the post-test nature of the loop. Even though the condition evaluates to `false` immediately, the execution block runs exactly once.
```php theme={"dark"}
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