Validating Strings as Alphanumeric Symbols Using Regex in PHP

2025-05-06 2025-05-06

Tak@

To check if a string contains only alphanumeric symbols using regular expressions, use ^[ -~]+$. This regular expression matches strings composed of one or more alphanumeric symbols, such as "Hello, world!". If you want to exclude spaces, modify the pattern to ^[!-~]+$.

Additionally, if you want to match a fixed-length alphanumeric string, use the pattern ^[ -~]{n}$. For example, ^[ -~]{6}$ matches a string exactly 6 characters long. You can also specify minimum and maximum lengths to create flexible patterns. For example, to match strings between 12 and 20 characters long, use ^[ -~]{12,20}$.

Below are some commonly used regular expression patterns for validating alphanumeric symbols. Feel free to utilize them as needed.

#	Match Condition	Regular Expression Pattern
1	Contains only alphanumeric symbols	^[ -~]+$
2	Fixed length of n alphanumeric symbols	^[ -~]{n}$
3	At least n alphanumeric symbols	^[ -~]{n,}$
4	No more than m alphanumeric symbols	^[ -~]{1,m}$
5	Between n and m alphanumeric symbols	^[ -~]{n,m}$

A list of common regular expression patterns for validating alphanumeric symbols

Source Code

Here is a PHP function to validate if an input string consists only of alphanumeric symbols. The function allows validation based on the following conditions:

If the minimum length is omitted: The string must consist only of alphanumeric symbols and not exceed the specified maximum length.
If the maximum length is omitted: The string must consist only of alphanumeric symbols and meet the minimum length requirement.
If both minimum and maximum lengths are omitted: The string must consist entirely of alphanumeric symbols.

/**
 * Checks whether a given string consists only of alphanumeric characters and symbols.
 *
 * This function verifies that the string consists only of alphanumeric characters
 * and symbols within the ASCII range (0x20 to 0x7E) and that its length falls
 * within the specified range.
 *
 * @param string $str The input string.
 * @param ?int $minLength The minimum number of characters (treated as 1 if null).
 * @param ?int $maxLength The maximum number of characters (treated as the length of the string if null).
 * @return bool Returns true if the input string meets the conditions; otherwise, returns false.
 * @throws InvalidArgumentException Throws an exception if the minimum length is less than 1,
 * or if the maximum length is less than the minimum length.
 */
function isAlphanumericSymbols(string $str, ?int $minLength = null, ?int $maxLength = null): bool {
    // Set default values
    $min = $minLength ?? 1;
    $max = $maxLength ?? mb_strlen($str);

    // Validate arguments
    if ($min < 1) {
        // Throw an exception if the minimum length is less than 1
        throw new InvalidArgumentException('The minimum length must be an integer greater than or equal to 1.');
    }

    if (!is_null($maxLength) && $max < $min) {
        // Throw an exception if the maximum length is less than the minimum length
        throw new InvalidArgumentException('The minimum length must not exceed the maximum length.');
    }

    // Construct the regular expression pattern for alphanumeric characters and symbols
    $pattern = is_null($maxLength)
        ? sprintf('/^[ -~]{%d,}$/', (int)$min) // No limit on the maximum number of characters
        : sprintf('/^[ -~]{%d,%d}$/', (int)$min, (int)$max);

    // Perform the validation using regular expressions
    return (bool)preg_match($pattern, $str);
}