PHP returns the length of the first string that matches the mask in the string

php editor Xigua introduces you to a common need: how to find the substring that matches a specific mask in the returned string and calculate its length. This problem involves string processing and logical judgment. Through PHP's built-in functions and some simple operations, we can easily implement this function. Next, let's dive into how to use PHP to achieve this requirement.

Get the length of the first substring that matches the mask in a string in PHP

In php, you can use the preg_match() function to get the first substring in a string that matches the given mask and return its length. The syntax is as follows:

int preg_match(string $pattern, string $subject, array &$matches = null, int $flags = 0, int $offset = 0): int

in:

• $pattern: The mask pattern to match.
• $subject: The string to search within.
• &$matches: An optional parameter used to store matching results.
• $flags: Flags to match the pattern (optional, default is 0).
• $offset: The offset to start searching from (optional, default is 0).

To get the length of the first substring in a string that matches the mask, you can follow the steps below:

1. Define the mask pattern: Write the mask pattern according to the string to be matched. For example, to match an alphanumeric string, you would use [a-zA-Z0-9] .
2. Call the preg_match() function: Use the preg_match() function to search for substrings in the string that match the mask. For example:

$string = "This is a sample string.";
$mask = "[a-zA-Z0-9] ";
$matches = [];
preg_match($mask, $string, $matches);

3. Get the matching results: If the match is successful, $matches The array will contain the matched substring. The first matching substring is stored in $matches[0].
4. Return the substring length: Get the length of $matches[0], which is the length of the substring that matches the mask for the first time.

The complete code example is as follows:

function get_first_matching_substring_length($string, $mask) {
$matches = [];
if (preg_match($mask, $string, $matches)) {
return strlen($matches[0]);
} else {
return -1;
}
}

$string = "This is a sample string.";
$mask = "[a-zA-Z0-9] ";
$length = get_first_matching_substring_length($string, $mask);

echo "Length of the first matching substring: $length";

Example output:

Length of the first matching substring: 4

have to be aware of is:

• If there is no substring matching the mask in the string, the preg_match() function will return 0, in which case -1 should be returned.
The
• $flags parameter can be used to specify additional matching options, such as ignoring case or matching on multiple lines.

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