String Functions

<?php
$str = "Hello, World!";

echo strlen($str);        // 13 — length
echo strtolower($str);    // hello, world!
echo strtoupper($str);    // HELLO, WORLD!
echo ucfirst("hello");    // Hello
echo ucwords("hello world"); // Hello World
echo str_word_count($str); // 2 — word count
?>

<?php
$str = "Hello, World!";

// Find position
echo strpos($str, "World");   // 7 — position of "World"
echo strrpos($str, "l");      // 10 — last position of "l"

// Check if contains
echo str_contains($str, "World");  // true (PHP 8)
echo str_starts_with($str, "Hello"); // true (PHP 8)
echo str_ends_with($str, "!");       // true (PHP 8)

// Replace
echo str_replace("World", "PHP", $str);  // Hello, PHP!
echo str_ireplace("hello", "Hi", $str);  // Hi, World! (case-insensitive)
?>

<?php
$str = "Hello, World!";

echo substr($str, 7);     // World! — from position 7
echo substr($str, 7, 5);  // World — 5 chars from position 7
echo substr($str, -6);    // World! — last 6 chars

// Trim whitespace
$padded = "   Hello   ";
echo trim($padded);    // "Hello"
echo ltrim($padded);   // "Hello   " (left trim)
echo rtrim($padded);   // "   Hello" (right trim)
?>

<?php
// Split string into array
$csv = "apple,banana,cherry";
$fruits = explode(",", $csv);
// ["apple", "banana", "cherry"]

// Join array into string
$joined = implode(" | ", $fruits);
// "apple | banana | cherry"

// Split into characters
$chars = str_split("Hello", 1);
// ["H", "e", "l", "l", "o"]
?>

<?php
// sprintf — format a string
$name = "John";
$age = 25;
$message = sprintf("My name is %s and I am %d years old.", $name, $age);
echo $message;  // My name is John and I am 25 years old.

// number_format — format numbers
echo number_format(1234567.891, 2);        // 1,234,567.89
echo number_format(1234567.891, 2, '.', ','); // 1,234,567.89

// Padding
echo str_pad("5", 3, "0", STR_PAD_LEFT);  // 005
?>