How do I check if a string contains a specific word in PHP?

To check if a string contains a specific word or substring in PHP, you can use one of the following methods:

1. Using strpos() (Case-Sensitive Check)

This method checks for the case-sensitive existence of a substring.

$string = "The quick brown fox jumps over the lazy dog";
$word = "fox";

if (strpos($string, $word) !== false) {
    echo "The string contains the word '$word'.";
} else {
    echo "The string does NOT contain the word '$word'.";
}

Notes:

• strpos() returns the position of the first occurrence of the substring (0 or higher) or false if not found.
• Use !== false for accurate checks (since 0 is a valid position and == false would incorrectly fail).

2. Using str_contains() (PHP 8.0+)

Simplifies substring checks with a direct boolean return (case-sensitive).

if (str_contains($string, $word)) {
    echo "The string contains '$word'.";
}

3. Case-Insensitive Check

To ignore case, use stripos() or combine strtolower() with str_contains().

Using stripos():

if (stripos($string, "FOX") !== false) {
    echo "Case-insensitive match found.";
}

Using str_contains() with strtolower() (PHP 8.0+):

if (str_contains(strtolower($string), strtolower($word))) {
    echo "Case-insensitive match found.";
}

4. Check for Whole Words (Regex)

Use regular expressions to ensure the substring is a whole word (not part of another word).

if (preg_match('/\b' . preg_quote($word, '/') . '\b/i', $string)) {
    echo "Exact word match found (case-insensitive).";
}

Explanation:

• \b marks a word boundary.
• i flag makes the search case-insensitive.
• preg_quote() escapes special regex characters in $word.

5. Using strstr()

Checks if a substring exists and returns part of the string (case-sensitive).

if (strstr($string, $word) !== false) {
    echo "Substring found.";
}

Summary

Method	Case-Sensitive	Returns	Best For
strpos()	✅ Yes	Position/false	General substring checks
str_contains()	✅ Yes	true/false	PHP 8.0+ simplicity
stripos()	❌ No	Position/false	Case-insensitive checks
Regex (preg_match)	Optional	1 (found)/0 (not)	Complex patterns/whole words

Best Practice

• For PHP 8.0+: Use str_contains() for simplicity.
• For older PHP versions: Use strpos() with strict !== false checks.
• For case-insensitive checks: Use stripos() or str_contains() with strtolower().
• For whole words: Use regex with preg_match() and word boundaries (\b).

By choosing the right method, you can efficiently check for substrings in PHP!