How to Check if a String Contains a Substring in PHP

To check if a string contains a substring in PHP, you can use several functions depending on your needs. Here are the most commonly used methods:

1. strpos() Function#

The strpos() function is commonly used to find the position of the first occurrence of a substring in a string. If the substring is found, it returns the position (index) of the first occurrence. If it’s not found, it returns false.

$string = "Hello, world!";
$substring = "world";

if (strpos($string, $substring) !== false) {
    echo "The substring '$substring' was found in the string.";
} else {
    echo "The substring '$substring' was not found in the string.";
}

Note: Use !== false to check if the result is exactly false, as strpos() can return 0 when the substring is found at the beginning of the string.

2. str_contains() Function (PHP 8.0+)#

Starting from PHP 8.0, you can use the str_contains() function, which simplifies the check and improves readability. It returns true if the substring is found, otherwise false.

$string = "Hello, world!";
$substring = "world";

if (str_contains($string, $substring)) {
    echo "The substring '$substring' was found in the string.";
} else {
    echo "The substring '$substring' was not found in the string.";
}

3. preg_match() Function#

You can also use regular expressions with preg_match(). This is useful if you need to perform more complex pattern matching.

$string = "Hello, world!";
$substring = "world";

if (preg_match("/" . preg_quote($substring, '/') . "/", $string)) {
    echo "The substring '$substring' was found in the string.";
} else {
    echo "The substring '$substring' was not found in the string.";
}

Note: preg_quote() is used to escape any special characters in the substring that might be interpreted as part of the regular expression.

Summary#

• strpos(): Use this for compatibility with PHP versions prior to 8.0. Be careful with 0 index positions.
• str_contains(): Use this for cleaner and more readable code in PHP 8.0 and later.
• preg_match(): Use this for more complex matching scenarios involving regular expressions.

Choose the method that best fits your needs based on PHP version and complexity of the substring search.