The **`ctype_cntrl` method** can be used to check if all the characters in the text are control characters.

# 
#  Syntax

```
ctype_cntrl(mixed $text): bool
```

This method returns a Boolean value.

The control characters are 

* `\0`: Null character.
* `\n`: New line character. 
* `\b`: Backspace character.
* `\t`: Horizontal tab character. 
* `\v`: Vertical tab character. 
* `\f`: Form field character.
* `\r`: Carriage return character. 
* `\e`: Escape character. 

>Read more about control characters [here](https://en.wikipedia.org/wiki/Control_character).

##  
## Example


<?php 

  $str = "\t";
  printIsControlCharacters($str);

  $str = "\n\r\t";
  printIsControlCharacters($str);

  $str = "123";
  printIsControlCharacters($str);
  
  $str = "a";
  printIsControlCharacters($str);

  function printIsControlCharacters($str){
    echo "The string is: ". $str. "\n";
    echo "Is Control Char: ";
    var_dump(ctype_cntrl($str));
    echo "---------\n";
  }

?>

In the code above: 

* We have used the `ctype_cntrl` method to check if the string contains only control characters. 

* For the string `\t` and `\n\r\t`, the `ctype_cntrl` returns `true`.

* For the string `123` and `a`, the `ctype_cntrl` method returns `false` because the string contains characters that are not control characters.

What is the ctype_cntrl method in PHP?

The `ctype_cntrl` method checks if a string contains only control characters, returning a Boolean value.