PHP Variable Handling

Variable Functions Overview

🔹 Checking Variable Types

Use type-checking functions to verify what kind of data a variable contains. This helps prevent errors and ensures your code handles data correctly.

<?php
$number = 42;
$text = "Hello";
$list = [1, 2, 3];

// Check if integer
echo is_int($number) ? "Yes, it's an integer" : "No";

// Check if string
echo "<br>" . (is_string($text) ? "Yes, it's a string" : "No");

// Check if array
echo "<br>" . (is_array($list) ? "Yes, it's an array" : "No");
?>

🔹 isset() and empty()

Check if variables are set and contain values. isset() checks if a variable exists, while empty() checks if it's empty or false.

<?php
$name = "John";
$age = 0;
$city = "";

// Check if variable is set
echo isset($name) ? "Name is set" : "Not set";

// Check if variable is empty
echo "<br>" . (empty($city) ? "City is empty" : "City has value");

// Zero is considered empty
echo "<br>" . (empty($age) ? "Age is empty" : "Age has value");
?>

🔹 Getting Variable Type

Use gettype() to find out what type of data a variable holds. This is useful for debugging and understanding your data structures.

<?php
$var1 = 100;
$var2 = "Hello";
$var3 = 3.14;
$var4 = true;
$var5 = null;

echo "var1 is: " . gettype($var1);
echo "<br>var2 is: " . gettype($var2);
echo "<br>var3 is: " . gettype($var3);
echo "<br>var4 is: " . gettype($var4);
echo "<br>var5 is: " . gettype($var5);
?>

🔹 Type Conversion

Convert variables from one type to another using conversion functions. This ensures data is in the correct format for operations and comparisons.

<?php
$text = "123";
$decimal = "45.67";

// Convert string to integer
$number = intval($text);
echo "Integer: " . $number . " (type: " . gettype($number) . ")";

// Convert string to float
$float = floatval($decimal);
echo "<br>Float: " . $float . " (type: " . gettype($float) . ")";

// Convert number to string
$str = strval(100);
echo "<br>String: " . $str . " (type: " . gettype($str) . ")";
?>

🔹 var_dump() and print_r()

Display detailed information about variables for debugging. var_dump() shows type and value, while print_r() displays human-readable information about arrays and objects.

<?php
$data = ["name" => "John", "age" => 30];

// Detailed variable information
echo "var_dump output:<br>";
var_dump($data);

// Human-readable format
echo "<br><br>print_r output:<br>";
print_r($data);
?>

🔹 is_null() and unset()

Check for null values and remove variables from memory. is_null() tests if a variable is null, while unset() destroys the variable completely.

<?php
$value = null;
$name = "John";

// Check if null
echo is_null($value) ? "Value is null" : "Value is not null";

// Unset a variable
unset($name);
echo "<br>" . (isset($name) ? "Name exists" : "Name was unset");
?>

🔹 is_numeric() and is_scalar()

Check if variables contain numeric values or scalar types. These functions help validate input and ensure data is in the expected format.

<?php
$num1 = 123;
$num2 = "456";
$text = "hello";

// Check if numeric (number or numeric string)
echo is_numeric($num1) ? "num1 is numeric" : "Not numeric";
echo "<br>" . (is_numeric($num2) ? "num2 is numeric" : "Not numeric");
echo "<br>" . (is_numeric($text) ? "text is numeric" : "Not numeric");

// Check if scalar (int, float, string, or bool)
echo "<br>" . (is_scalar($num1) ? "num1 is scalar" : "Not scalar");
?>