PHP:
Extracting substrings
How to:
PHP offers several functions to extract substrings. Let’s check out substr, mb_substr, and strstr.
$string = "Hello, World! Programming is fun.";
// Extract 'World' using substr.
echo substr($string, 7, 5); // Output: World
// UTF-8 string example with mb_substr for multi-byte characters.
$utf8String = "こんにちは世界";
echo mb_substr($utf8String, 5, 2); // Output: 世
// Get everything after the comma with strstr.
echo strstr($string, ","); // Output: , World! Programming is fun.
Deep Dive
Back in PHP’s early days, the main way to snatch a piece of a string was substr(). However, substr() had (and still has) a limit: it doesn’t play well with non-English characters (like Japanese or Arabic).
Enter mb_substr(), the multibyte-safe counterpart that respects characters from various encodings. It ensures that when you yank a substring, you’re not tearing through a character mid-byte, which is crucial for international applications.
strstr(), on the other hand, finds the first occurrence of a substring and gives you everything after it. There’s also strchr() which is an alias of strstr().
While substr() and mb_substr() let you specify precisely where to start and how much to take, strstr() is more like a “find and give me the rest” tool.
See Also
Here’s some extra reading if you’re hungry for more:
- PHP Official Documentation for string functions: https://www.php.net/manual/en/ref.strings.php
- A deep dive into PHP’s multibyte string functions: https://www.php.net/manual/en/book.mbstring.php
- More about character encoding and why it matters: http://kunststube.net/encoding/