> ## 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 Elseif Clause
The `elseif` clause is a conditional control structure chained after an `if` block as part of a broader `if` statement. It executes its associated statement block only if the preceding `if` condition, and any preceding `elseif` conditions, evaluate to `false`, and its own condition evaluates to `true`.
## Standard Syntax
In standard PHP syntax using curly braces, `elseif` is declared immediately following the closing brace of the preceding `if` or `elseif` block.
```php theme={"dark"}
if ($expression1) {
// Executes if $expression1 is true
} elseif ($expression2) {
// Executes if $expression1 is false AND $expression2 is true
} elseif ($expression3) {
// Executes if $expression1 and $expression2 are false AND $expression3 is true
} else {
// Executes if all preceding expressions are false
}
```
## Execution Mechanics
1. **Sequential Evaluation:** The PHP engine evaluates the expressions strictly in the order they appear.
2. **Boolean Context:** Every expression passed to an `elseif` is implicitly cast to a boolean value (`true` or `false`) prior to evaluation.
3. **Short-circuiting:** Once an `if` or `elseif` condition evaluates to `true`, its corresponding block is executed, and the engine immediately exits the entire control structure. Subsequent `elseif` conditions are never evaluated.
## `elseif` vs. `else if`
PHP supports both the single-word `elseif` and the two-word `else if`. When using standard curly brace syntax, their behavior is functionally identical.
However, at the parser level, `else if` (two words) is treated as an entirely new `if` statement nested implicitly within the `else` block of the preceding condition.
```php theme={"dark"}
// This:
if ($a) {
} else if ($b) {
}
// Is parsed identically to this:
if ($a) {
} else {
if ($b) {
}
}
```
## Alternative Syntax Constraints
PHP offers an alternative syntax for control structures using colons (`:`) and an `endif;` terminator. When utilizing this alternative syntax, **you must use the single-word `elseif`**.
Using the two-word `else if` in the alternative syntax will result in a fatal parse error.
**Valid Alternative Syntax:**
```php theme={"dark"}
if ($expression1):
// statements
elseif ($expression2):
// statements
else:
// statements
endif;
```
**Invalid Alternative Syntax (Throws Parse Error):**
```php theme={"dark"}
if ($expression1):
// statements
else if ($expression2): // Parse error: syntax error, unexpected token "if", expecting ":"
// statements
endif;
```
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