Are there any built-in PHP functions that can be used to efficiently check if a string meets certain criteria, such as containing only alphanumeric characters?

To efficiently check if a string contains only alphanumeric characters in PHP, you can use the built-in function `ctype_alnum()`. This function returns true if all characters in the string are alphanumeric (letters or digits) and false otherwise. By using this function, you can easily validate a string against the desired criteria. 

$string = "Hello123";
if (ctype_alnum($string)) {
    echo "String contains only alphanumeric characters.";
} else {
    echo "String contains non-alphanumeric characters.";
}

Keywords

PHP built-in functions string alphanumeric characters criteria

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