Expressions
Why Use Expressions?
Some functions, like the incredibly useful $if function, require an expression as input. Expressions allow you to create dynamic and conditional logic within your scripts.
What is an Expression?
At its core, an expression compares a left-hand side to a right-hand side using an operator. The operator dictates the type of comparison being made.
Left-Side [Operator] Right-Side
Here's a breakdown of the available operators:
| Operator | True When | Description |
|---|---|---|
== | left-side is equal to right-side | Checks for equality. Both values are compared after normalizing whitespace (leading and trailing spaces are ignored). |
=== | left-side is exactly equal to right-side | Checks for exact equality. Values must match exactly, including any leading or trailing whitespace. |
!= | left-side is not equal to right-side | Checks for inequality. Both values are compared after normalizing whitespace (leading and trailing spaces are ignored). |
!== | left-side is not exactly equal to right-side | Checks for exact inequality. Values are considered different if they do not match exactly, including any leading or trailing whitespace. |
> | left-side is greater than right-side (numeric) | Left-side is numerically greater than the right-side. |
>= | left-side is greater than or equal to right-side (numeric) | Left-side is numerically greater than or equal to the right-side. |
< | left-side is less than right-side (numeric) | Left-side is numerically less than the right-side. |
<= | left-side is less than or equal to right-side (numeric) | Left-side is numerically less than or equal to the right-side. |
&& | left-side is true and right-side is true | Logical AND. Both sides must evaluate to true. |
|| | left-side is true or right-side is true | Logical OR. At least one side must evaluate to true. |
Example:
$username==Mido
In this expression:
- Left-side:
$username - Right-side:
Mido - Operator:
==
This expression evaluates to true only if the value of the variable $username is equal to Mido.
Combining Multiple Expressions
Often, you'll need to create more complex conditions by combining multiple expressions. This is where the && (AND) and || (OR) operators become essential.
Example 1: Using AND (&&)
$username==Mido&&$country==Egypt
This expression consists of two separate conditions:
$username==Mido: The username must be equal to "Mido".$country==Egypt: The country must be equal to "Egypt".
The && operator means that both condition 1 AND condition 2 must be true for the entire expression to evaluate to true.
Example 2: Using OR (||)
$username==Mido||$country==Egypt
This expression also consists of two separate conditions:
$username==Mido: The username must be equal to "Mido".$country==Egypt: The country must be equal to "Egypt".
The || operator means that either condition 1 OR condition 2 (or both) must be true for the entire expression to evaluate to true.
Grouping Expressions with Parentheses
For advanced scenarios, you may need to control the order in which expressions are evaluated. Use parentheses () to group conditions and ensure they are evaluated as a unit before other operations. This is similar to how parentheses work in mathematical equations.
Example 1: Complex AND/OR Grouping
($username==Mido&&$country==Egypt)||($username==Rake&&$country==Germany)
This expression combines AND and OR operators with grouping:
($username==Mido&&$country==Egypt): The username is "Mido" AND the country is "Egypt".($username==Rake&&$country==Germany): The username is "Rake" AND the country is "Germany".
The entire expression evaluates to true if either group 1 OR group 2 is true.
Example 2: Nested OR Grouping
$username==Mido||($country==Egypt||$country==Masr)
This example uses nested parentheses with OR operators:
$username==Mido: The username is "Mido".($country==Egypt||$country==Masr): The country is "Egypt" OR the country is "Masr".
The expression is true if the username is "Mido" OR if the country is either "Egypt" or "Masr".