การค้นหาและแทนที่ในสตริง

<?php
$str = 'the quick brown fox';

$pos = strpos($str, 'brown');
echo $pos;  // 10

// Always use === to check for false (0 is also falsy!)
if (strpos($str, 'quick') !== false) {
    echo 'Found!';
}

<?php
$email = 'user@example.com';

var_dump(str_contains($email, '@'));        // true
var_dump(str_starts_with($email, 'user'));  // true
var_dump(str_ends_with($email, '.com'));    // true
var_dump(str_ends_with($email, '.org'));    // false

<?php
$template = 'Hello {name}, your order #{id} is ready.';

$result = str_replace(
    ['{name}', '{id}'],
    ['Alice',  '4521'],
    $template
);

echo $result;
// Hello Alice, your order #4521 is ready.

<?php
$text = 'PHP is great. php is powerful. PHP is fun.';

$result = str_ireplace('php', 'PHP 8', $text);
echo $result;
// PHP 8 is great. PHP 8 is powerful. PHP 8 is fun.

<?php
$str = 'Hello World';

echo substr_replace($str, 'PHP', 6, 5);
// Hello PHP

// Replace from end
echo substr_replace($str, '!', -1);
// Hello Worl!

<?php
$text = 'to be or not to be';

echo substr_count($text, 'be');   // 2
echo substr_count($text, 'to');   // 2
echo substr_count($text, 'or');   // 1

<?php
$html = '<p>Hello <b>World</b></p>';

// Strip HTML tags
$plain = preg_replace('/<[^>]+>/', '', $html);
echo $plain;  // Hello World

// Replace multiple spaces with one
$spaced = 'too   many    spaces';
echo preg_replace('/\s+/', ' ', $spaced);
// too many spaces

<?php
$userInput = '<script>alert("hacked")</script>';

// Dangerous:
echo $userInput; // executes script!

// Safe:
echo htmlspecialchars($userInput, ENT_QUOTES, 'UTF-8');
// &lt;script&gt;alert(&quot;hacked&quot;)&lt;/script&gt;

<?php
$text = 'cat and cat and cat';
$count = 0;
$result = str_replace('cat', 'dog', $text, $count);

echo $result;  // dog and dog and dog
echo $count;   // 3

<?php
echo str_pad('42', 8);           // '42      ' (right-pad)
echo str_pad('42', 8, '0', STR_PAD_LEFT);  // '000042'
echo str_pad('PHP', 7, '-', STR_PAD_BOTH); // '--PHP--'