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

In PHP, a string is a sequence of characters enclosed within single quotes (”) or double quotes (“”). Strings are one of the fundamental data types in PHP and play a significant role in various aspects of programming. They are used to store and manipulate textual data, such as names, sentences, URLs, and more.

Understanding strings in PHP is important for effectively working with textual data and building robust applications. With the ability to manipulate and process strings, PHP developers can create dynamic and interactive web pages, handle user input securely and can perform various data operations efficiently.

Using strpos() Function

The strpos() function in PHP is used to find the position of the first occurrence of a specific substring within a given string. It stands for “string position.” The purpose of strpos() is to determine the starting index of a substring within a larger string.

strpos(string $haystack, mixed $needle, int $offset = 0): int|false

The strpos() function returns the numeric position of the first occurrence of the substring within the haystack. If the substring is not found, it returns false.

$string = "Hello, how are you?";
$word = "how";

$position = strpos($string, $word);
echo "The word \"$word\" starts at position: $position";

Utilizing strstr() Function

The strstr() function in PHP is used to find the first occurrence of a substring within a given string. It stands for “string to string.” The purpose of strstr() is to locate a substring within a larger string and return the portion of the string starting from the first occurrence of the substring.

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

The strstr() function returns a substring of the haystack starting from the first occurrence of the needle. If the substring is not found, it returns false.

$string = "Hello, how are you?";
$substring = strstr($string, "how");

echo "The remaining string after \"how\" is: $substring";

Output: The remaining string after "how" is: how are you?

The strstr() function and the strpos() function are similar in that they both involve searching for substrings within a string, but they differ in their return values and usage.

Exploring preg_match() Function

In PHP, the preg_match() function is used for pattern matching with regular expressions. It allows you to search for complex patterns within a given string. The term “preg” stands for “Perl-Compatible Regular Expression,” indicating that PHP’s regular expression functions are based on Perl’s syntax.

$string = "Hello, how are you?";
$pattern = "/how/";

$result = preg_match($pattern, $string);
if ($result === 1) {
echo "The string contains the word 'how'.";
} else {
echo "The string does not contain the word 'how'.";
}

Output: The string contains the word ‘how’.

Implementing substr_count() Function

In PHP, the substr_count() function is used to count the number of occurrences of a substring within a given string. It calculates the frequency of a specific substring in a larger string and returns the count.

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

$count = substr_count(strtolower($string), strtolower($word));
echo "The word \"$word\" occurs $count times.";

Output: The word “the” occurs 2 times.

By understanding the syntax, practical applications, and performance considerations of substr_count(), you can effectively utilize this function in PHP to count the occurrences of a substring within a string.