PHP | ctype_cntrl() Function

The ctype_cntrl() function is an inbuilt function in PHP and is used to check if all the characters of a given string are control characters or not. It returns True if all characters of the string are control characters otherwise it returns false.
Control Character: A character that does not represent a printable character but serves to initiate a particular action. For example ‘\n’ is a control character that is not printable but performs the action “Next Line”.
Syntax:

ctype_cntrl( $text )

Parameters: The function accepts a single parameter $text which represents the input string.
Return Value: This function returns TRUE if all characters of the string are Control Character otherwise it returns FALSE.
Examples: 

Input  : "\t"
Output : Yes

Input  : "\\\b"
Output : No                 

Below programs illustrate the ctype_cntrl() function: 
Program: 1

PHP

<?php
// PHP program to check given string has all
// characters as control character

$string = "\n";

// Checking above given strings
// by used of ctype_cntrl() function
if ( ctype_cntrl($string))
    echo "Yes\n";
else
    // if False then return No
    echo "No\n";
?>

Output:

Yes

Program: 2

PHP

<?php
// PHP program to illustrate the ctype_cntrl() function

$strings = array("\c", "\f", "\n", "\\","123","GFG");

// Checking above given strings
// by use of ctype_cntrl() function .
foreach ($strings as $test) {

    if ( ctype_cntrl($test))
        echo "Yes\n";
    else
        echo "No\n";
}
?>

Output:

No
Yes
Yes
No
No
No

Reference: http://php.net/manual/en/function.ctype-cntrl.php