PHP, Structures and Functions, STRINGS

This function a one-character string containing the character specified by interpreting $bytevalue as an unsigned integer.

This can be used to create a one-character string in a single-byte encoding such as ASCII, ISO-8859, or Windows 1252, tby passing the position of a desired character in the encoding's mapping table.

However, note that this function is not aware of any string encoding, and in particular cannot be passed a Unicode code point value to generate a string in a multibyte encoding like UTF-8 or UTF-16.

This function complements ord.


<?php

str chr ( int $bytevalue )


where,

$bytevalue = An integer between 0 and 255

?>

$bytevalue

An integer between 0 and 255.

EXERCISE


<table width="100%" cellspacing="5" cellpadding="5" 
border="1" align="center"> 
<tbody><tr><td colspan="2">ord/chr</td></tr><tr> 
<td width="30%">ord</td><td>chr</td></tr> 

<?php

for ($ord01 = 0; $ord01 <= 255; $ord01++)
{
echo '<tr><td>' . $ord01 . '</td><td>' . chr($ord01) . '</td></tr>';     
} 

?> 
<tr><td colspan="2">ed48</td></tr></tbody></table>

EXERCISE


<?php

echo "Testing chr() : basic functionality.<br><br>";

echo chr(72). chr(101) . chr(108) . chr(108). chr(111); 
// Hello
echo chr(10); 
// "<br>"
echo "World";

?>

RESULT

Testing chr() : basic functionality.

Hello World

EXERCISE


<?php

echo "Testing chr() function: 
                  with unexpected inputs for 'ascii' argument.";

//get an unset variable
$unset_var = 'string_val';
unset($unset_var);

//defining a class
class sample  {
  public function __toString() {
    return "sample object";
  }
}

//getting the resource
$file_handle = fopen(__FILE__, "r");

// array with different values for $input
$inputs =  array (

          // integer values
/*1*/      0,
          1,
          255,
          256,

          // float values
/*5*/      10.5,
          -20.5,
          1.1234e6,

          // boolean values
/*11*/      true,
          false,
          TRUE,
          FALSE,

          // null values
/*15*/      NULL,
          null,

          // undefined variable
/*19*/      @$undefined_var,

          // unset variable
/*20*/      @$unset_var
);

// loop through with each element 
// of the $inputs array to test chr() function
$count = 1;
foreach($inputs as $input) {
  echo "<br><br>Iteration: $count<br>";
  var_dump( bin2hex(chr($input)) );
  $count ++;
}

fclose($file_handle);  
//closing the file handle

?>