Constant vs Variables
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Constant vs Variables
Constants and variables are both used to store values in PHP, but they have some important differences.
- Value: The value of a variable can be changed during the execution of a script, whereas the value of a constant cannot be changed once it is defined.
$x = 10;
$x = 20; // Valid
define("PI", 3.14);
PI = 3.15; // Invalid
- Scope: Variables can have different scopes, such as global scope or local scope, depending on where they are defined, while constants are always defined globally.
define("PI", 3.14);
function calculate_area($radius) {
$area = PI * $radius * $radius;
echo $area;
}
calculate_area(5); // output: 78.5
- Naming convention: Constants are conventionally named in uppercase letters, while variables are named in lowercase or camelCase.
3. Naming convention: Constants are conventionally named in uppercase letters, while variables are named in lowercase or camelCase.
- Purpose: Constants are typically used for values that are unlikely to change during the execution of a script, such as mathematical constants or configuration values. Variables, on the other hand, are used for values that can change during the execution of a script, such as user input or the result of a calculation.
define("MAX_SIZE", 1024);
$filename = "example.txt";
$file_size = filesize($filename);
if ($file_size > MAX_SIZE) {
echo "File size exceeds maximum limit";
} else {
// Process the file
}
In general, it’s a good practice to use constants for values that should not be changed during the execution of a script, and variables for values that can change. This can help make your code more readable and maintainable.
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