What are some common mistakes to avoid when working with PHP strings?

One common mistake when working with PHP strings is forgetting to properly escape characters, especially when dealing with user input. This can lead to security vulnerabilities like SQL injection attacks. To avoid this, always sanitize and validate user input before using it in a string. 

$user_input = $_POST['user_input'];
$clean_input = htmlspecialchars($user_input, ENT_QUOTES, 'UTF-8');
echo "User input: " . $clean_input;
```

Another mistake is not properly handling multibyte characters, which can lead to unexpected behavior or errors. To handle multibyte characters correctly, use functions like mb_strlen() and mb_substr() instead of their single-byte counterparts.

```php
$string = "こんにちは";
echo "Length: " . mb_strlen($string);
echo "Substring: " . mb_substr($string, 0, 3);
```

Lastly, be cautious when using functions like strpos() or substr() with strings that may contain special characters or UTF-8 encoding. Always use multibyte-safe alternatives like mb_strpos() or mb_substr() to ensure proper handling of multibyte characters.

```php
$string = "café";
$position = mb_strpos($string, 'é');
if ($position !== false) {
    echo "Found 'é' at position: " . $position;
} else {
    echo "'é' not found in the string.";
}

Keywords

concatenation strlen substr trim strpos

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