المتغيرات وأنواع البيانات

<?php
$name = "John";       // String
$age = 25;            // Integer
$height = 1.75;       // Float
$isStudent = true;    // Boolean
?>

<?php
$name = "John";
$age = 25;
$price = 19.99;
$isValid = true;
$nothing = null;

var_dump($name);     // string(4) "John"
var_dump($age);      // int(25)
var_dump($price);    // float(19.99)
var_dump($isValid);  // bool(true)
var_dump($nothing);  // NULL
?>

<?php
$s1 = 'PHP Tutorial';       // Single quotes: literal string, no variable parsing
$s2 = "PHP Tutorial";       // Double quotes: parses variables and escape sequences

$name = "John";
echo 'Hello $name';         // Hello $name  — single quotes don't parse variables
echo "Hello $name";         // Hello John   — double quotes parse variables
?>

<?php
$name = "John";

// Single quotes: output exactly as written
echo 'Hello, $name!\nNice weather today.';
// Output: Hello, $name!\nNice weather today.

// Double quotes: parse variables and escape sequences
echo "Hello, $name!\nNice weather today.";
// Output: Hello, John! (newline) Nice weather today.
?>

<?php
$decimal = 42;         // Decimal
$hex = 0x2A;           // Hexadecimal (=42)
$octal = 052;          // Octal (=42)
$binary = 0b101010;    // Binary (=42)

$float1 = 3.14;        // Float
$float2 = 1.2e3;       // Scientific notation = 1200
$float3 = 7E-10;       // Scientific notation = 0.0000000007
?>

<?php
$isLogin = true;
$isAdmin = false;

if ($isLogin) {
    echo "Welcome back!";
}
?>

<?php
$name = "John";
$age = 25;

var_dump(is_string($name));   // bool(true)
var_dump(is_int($age));       // bool(true)
var_dump(is_float($age));     // bool(false)
var_dump(is_bool($age));      // bool(false)
var_dump(is_array($name));    // bool(false)

// gettype() returns the type name (for debugging, not logic)
echo gettype($name);  // string
?>

<?php
// Automatic conversion
$result = "10" + 5;         // 15 ("10" converted to number)
$text   = "10" . 5;         // "105" (5 converted to string)

// Explicit conversion
$intVal   = (int) "123";    // 123
$floatVal = (float) "3.14"; // 3.14
$strVal   = (string) 123;   // "123"
$boolVal  = (bool) 1;       // true
?>

<?php
// String to number
$a = (int) "42";
echo $a + 8;  // 50

// Number to string
$b = (string) 100;
echo "Price: " . $b . " yuan";  // Price: 100 yuan

// Boolean conversion rules: these values are treated as false
echo (int)((bool)0);     // 0
echo (int)((bool)"");    // 0
echo (int)((bool)[]);    // 0
echo (int)((bool)null);  // 0
// All other values are true
?>

<?php
$var1 = "Hello";
$var2 = null;

// isset(): variable is set and not null → true
var_dump(isset($var1));       // bool(true)
var_dump(isset($var2));       // bool(false)
var_dump(isset($notExist));   // bool(false) — doesn't exist

// empty(): variable is empty → true ("", 0, "0", null, false, [] are all "empty")
var_dump(empty($var1));       // bool(false) — "Hello" is not empty
var_dump(empty($var2));       // bool(true)  — null is empty
var_dump(empty(0));           // bool(true)  — 0 is considered empty!
var_dump(empty($notExist));   // bool(true)  — not existing is also considered empty
?>

<?php
function testVar(string $label, mixed $value): void {
    echo "$label — isset: " . (isset($value) ? 'true' : 'false');
    echo " | empty: " . (empty($value) ? 'true' : 'false') . "<br>";
}

testVar('"Hello"', "Hello");
testVar('""', "");
testVar('0', 0);
testVar('null', null);
// Observe the isset and empty results for each value
?>