Strings

<?php
$name = "Asha";
$qty = 3;

echo 'Hi $name\n', "\n";        // single: no interpolation, no \n
echo "Hi $name, you have $qty items\n";
echo "Tab:\tafter tab | quote: \" | dollar: \$name\n";

// arrays and objects: use braces for anything beyond a plain variable
$user = ['name' => 'Ravi', 'langs' => ['php', 'sql']];
echo "User: {$user['name']}, first language: {$user['langs'][0]}\n";
echo "Simple syntax works for one level: $user[name]\n";

$order = new stdClass();
$order->id = 1042;
$order->total = 59.5;
echo "Order #{$order->id} costs {$order->total}\n";

$item = "apple";
echo "Two {$item}s\n";          // braces mark where the name ends

<?php
$name = "Asha";
$total = 59.5;

$email = <<<TEXT
    Hi $name,
    Your order total is {$total} rupees.
      (This line keeps 2 extra spaces.)
    "Quotes" need no escaping.
    TEXT;
echo $email, "\n---\n";

$template = <<<'RAW'
    Dear $name, nothing is replaced in a nowdoc.
    RAW;
echo $template, "\n";

<?php
$first = "Ada";
$last = "Lovelace";
echo $first . " " . $last . "\n";

$price = 10;
echo "Total: " . $price + 5, "\n";      // PHP 8: + happens first
echo "Sum: " . ($price + 5) . "\n";     // brackets say it clearly

$csv = "";
foreach (['id', 'name', 'email'] as $col) {
    $csv .= $col . ",";
}
echo rtrim($csv, ","), "\n";            // trim the trailing comma

// usually cleaner: build an array, join once
$parts = [];
foreach ([3, 1, 2] as $n) {
    $parts[] = "#$n";
}
echo implode(" ", $parts), "\n";
echo str_repeat("=-", 5), "\n";

<?php
$s = "  Learn PHP the right way  ";
$t = trim($s);                         // also ltrim / rtrim

echo "[$t] length ", strlen($t), "\n";
var_dump(str_contains($t, "PHP"));     // PHP 8
var_dump(str_starts_with($t, "Learn"), str_ends_with($t, "way"));

echo substr($t, 6, 3), "\n";          // from index 6, 3 chars
echo substr($t, -3), "\n";            // last 3
echo strtoupper($t), " | ", strtolower("PHP"), "\n";
echo ucfirst("hello world"), " | ", ucwords("hello world"), "\n";

echo str_replace("right", "modern", $t), "\n";
echo str_replace(["a", "e"], "*", "banana tree", $count), " ($count replaced)\n";

$csv = "red,green,,blue";
$colors = explode(",", $csv);          // string -> array
echo count($colors), " parts: ", implode(" | ", $colors), "\n";
print_r(explode(",", $csv, 2));        // limit: at most 2 parts

<?php
$email = "[email protected]";

$pos = strpos($email, "admin");
echo $pos !== false ? "found at $pos\n" : "not found\n";

$at = strpos($email, "@");
echo "user: ", substr($email, 0, $at), ", domain: ", substr($email, $at + 1), "\n";

var_dump(strpos($email, "root"));      // false, not -1
var_dump(stripos($email, "ADMIN"));    // case-insensitive
var_dump(strrpos("a.b.c", "."));       // last occurrence
var_dump(str_contains($email, "admin"));

<?php
$item = "Keyboard";
$qty = 3;
$price = 49.5;

printf("%s x %d = %.2f\n", $item, $qty, $qty * $price);
echo sprintf("%05d", 42), "\n";          // zero-pad to width 5
echo sprintf("[%8s]", "right"), "\n";    // right-align in 8
echo sprintf("[%-8s]", "left"), "\n";    // left-align in 8
echo sprintf("%'.10d", 7), "\n";          // custom pad character
echo sprintf("%+d %+d", 5, -5), "\n";    // always show the sign
echo sprintf("%b %o %x %X", 10, 10, 255, 255), "\n";
echo sprintf("%.1f%%", 12.345), "\n";     // %% is a literal %
echo sprintf('%2$s, %1$s', "Ada", "Lovelace"), "\n"; // argument order

echo number_format(1234567.891), "\n";          // 0 decimals, rounded
echo number_format(1234567.891, 2), "\n";
echo number_format(1234567.891, 2, ",", "."), "\n"; // European style

<?php
$word = "café";
echo strlen($word), " bytes, ", mb_strlen($word), " characters\n";

echo strtoupper($word), " vs ", mb_strtoupper($word), "\n";
echo ucfirst("élan"), " vs ", mb_ucfirst("élan"), "\n";   // PHP 8.4+

$city = "München";
echo mb_substr($city, 0, 4), "\n";           // first 4 characters
echo count(str_split($city)), " byte chunks vs ",
     count(mb_str_split($city)), " characters\n";
echo implode("", array_reverse(mb_str_split($city))), "\n"; // safe reverse

$hindi = "नमस्ते";
echo strlen($hindi), " bytes, ", mb_strlen($hindi), " code points, ",
     grapheme_strlen($hindi), " visible characters\n";

<?php
var_dump("1e3" == "1000");          // numeric strings: compared as numbers
var_dump("1e3" === "1000");         // strict: different strings
var_dump("abc" == "ABC");           // case matters
var_dump(strcasecmp("HELLO", "hello") === 0);

echo strcmp("apple", "banana"), " ", "b" <=> "a", "\n";

$files = ["img12.png", "img10.png", "img2.png"];
sort($files);                        // byte by byte
echo implode(" ", $files), "\n";
usort($files, 'strnatcmp');          // "natural" order
echo implode(" ", $files), "\n";

// comparing secrets: constant-time, strict
$expected = "a1b2c3";
$given = "a1b2c3";
var_dump(hash_equals($expected, $given));

<?php
$text = "Invoice 7781 is due on 2026-03-15";

if (preg_match('/(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/', $text, $m)) {
    echo "Day {$m['day']}, month {$m['month']}, year {$m['year']}\n";
    echo "Whole match: {$m[0]}\n";
}

preg_match_all('/#(\w+)/', "Learn #php and #regex today", $tags);
echo implode(", ", $tags[1]), "\n";

echo preg_replace('/\s+/', ' ', "too    many     spaces"), "\n";
echo preg_replace('/(\w+)@(\w+)\.com/', '$1 at $2', "mail [email protected]"), "\n";
print_r(preg_split('/[\s,]+/', "red, green  blue,yellow"));

var_dump(preg_match('/^\w+$/', "café"), preg_match('/^\w+$/u', "café"));