Understanding PHP's strstr() Function: Syntax, Usage, and Examples

PHP is a widely used server‑side scripting language; one of its useful string functions is strstr(), which searches for the first occurrence of a needle in a haystack.

Syntax

strstr(string $haystack, mixed $needle, bool $before_needle = false): string|false

The function takes three parameters: the haystack string, the needle string, and an optional boolean indicating whether to return the part before the needle.

Usage examples

1. Find first occurrence

$haystack = "Hello World!";<br>$needle = "World";<br>$result = strstr($haystack, $needle);<br>echo $result;

This outputs World! because the substring from the needle to the end is returned.

2. Get text before the needle

$haystack = "Hello World!";<br>$needle = "World";<br>$result = strstr($haystack, $needle, true);<br>echo $result;

The output is Hello, the part preceding the needle.

3. Case‑sensitive search

By default strstr() is case‑sensitive. Searching for "world" would fail.

Case‑insensitive search

$haystack = "Hello World!";<br>$needle = "world";<br>$result = stristr($haystack, $needle);<br>echo $result;

This outputs World! using stristr().

4. Multibyte characters

For UTF‑8 strings, mb_strstr() should be used.

$haystack = "你好，世界！";<br>$needle = "世界";<br>$result = mb_strstr($haystack, $needle);<br>echo $result;

The result is 世界！.

Summary

The strstr() function is versatile for locating substrings, extracting text before a needle, performing case‑insensitive searches with stristr(), and handling multibyte data via mb_strstr(), making it valuable for PHP developers.