Answers by Sentry

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

Nadia S.

The Problem

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

The Solution

Since PHP 8, we can use the str_contains() function to check if a substring is present within a given string. In this example, we check whether a string URL has the http:// protocol:

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$url = "http://www.example.com/info/about-us";
$protocol = 'http://';

// check $url for the presence of the $protocol substring
echo str_contains($url, $protocol);

The function returns 1 for true:

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1

You can use an if statement to echo out a string literal of the result, for example:

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if (str_contains($url, $protocol)) {
    echo 'true';
} else {
    echo 'false';
}

Output:

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true

The strpos() function

Versions of PHP previous to PHP 8 use the less intuitive strpos() function to determine if a string contains a certain substring.

The strpos() function returns an integer of the substring’s starting position if the substring is present, for example:

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$url = "http://www.example.com/info/about-us";
$protocol = 'http://';

$ans = strpos($url, $protocol);
echo $ans;

The output tells us that $protocol is present and begins at the first character of $url:

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// index value
0

In contrast to str_contains(), you need to explicitly include a comparator in an if statement, such as $foo === false. For example:

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if ($ans === false) {
  echo "The string '$protocol' is NOT in '$url'";
} else {
  echo "The string '$protocol' is in '$url'";
}

Output:

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The string 'http://' is in 'http://www.example.com/info/about-us'

Note that you must use the === comparator instead of == if there is any chance of the substring in question starting at index 0 or the value of 0 will be interpreted as equating to false. So this example:

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if ($ans == false) {
  echo "The string '$protocol' is NOT in '$url'";
} else {
  echo "The string '$protocol' is in '$url'";
}

Will return:

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The string 'http://' is NOT in 'http://www.example.com/info/about-us'

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