openssl_random_pseudo_bytes(3) [php man page]

OPENSSL_RANDOM_PSEUDO_BYTES(3)						 1					    OPENSSL_RANDOM_PSEUDO_BYTES(3)

openssl_random_pseudo_bytes - Generate a pseudo-random string of bytes

SYNOPSIS

       string openssl_random_pseudo_bytes (int	$length, [bool	&$crypto_strong])

DESCRIPTION

	Generates a string of pseudo-random bytes, with the number of bytes determined by the $length parameter.

	It  also  indicates  if  a  cryptographically strong algorithm was used to produce the pseudo-random bytes, and does this via the optional
       $crypto_strong parameter. It's rare for this to be FALSE, but some systems may be broken or old.

PARAMETERS

	      o $length
		- The length of the desired string of bytes. Must be a positive integer. PHP will try to cast this parameter to a non-null integer
		to use it.

	      o $crypto_strong
		-  If  passed  into  the  function,  this  will  hold a boolean value that determines if the algorithm used was "cryptographically
		strong", e.g., safe for usage with GPG, passwords, etc.  TRUE if it did, otherwise FALSE

RETURN VALUES

	Returns the generated string of bytes on success, or FALSE on failure.

EXAMPLES

       Example #1

	      openssl_random_pseudo_bytes(3) example

	      <?php
	      for ($i = -1; $i <= 4; $i++) {
		  $bytes = openssl_random_pseudo_bytes($i, $cstrong);
		  $hex	 = bin2hex($bytes);

		  echo "Lengths: Bytes: $i and Hex: " . strlen($hex) . PHP_EOL;
		  var_dump($hex);
		  var_dump($cstrong);
		  echo PHP_EOL;
	      }
	      ?>

	      The above example will output something similar to:

	      Lengths: Bytes: -1 and Hex: 0
	      string(0) ""
	      NULL

	      Lengths: Bytes: 0 and Hex: 0
	      string(0) ""
	      NULL

	      Lengths: Bytes: 1 and Hex: 2
	      string(2) "42"
	      bool(true)

	      Lengths: Bytes: 2 and Hex: 4
	      string(4) "dc6e"
	      bool(true)

	      Lengths: Bytes: 3 and Hex: 6
	      string(6) "288591"
	      bool(true)

	      Lengths: Bytes: 4 and Hex: 8
	      string(8) "ab86d144"
	      bool(true)

SEE ALSO 
random_bytes(3), bin2hex(3), crypt(3), mt_rand(3), uniqid(3).
PHP Documentation Group 											    OPENSSL_RANDOM_PSEUDO_BYTES(3)

EMPTY(3)								 1								  EMPTY(3)

empty - Determine whether a variable is empty

SYNOPSIS

       bool empty (mixed  $var)

DESCRIPTION

	Determine  whether a variable is considered to be empty. A variable is considered empty if it does not exist or if its value equals FALSE.
       empty(3) does not generate a warning if the variable does not exist.

PARAMETERS

	      o $var
		- Variable to be checked

	      Note

		      Prior to PHP 5.5, empty(3) only supports variables; anything else will result in a parse error. In other words, the  follow-
		     ing will not work: empty(trim($name)). Instead, use trim($name) == false.

	       No  warning  is generated if the variable does not exist. That means empty(3) is essentially the concise equivalent to !isset($var)
	      || $var == false.

RETURN VALUES

	Returns FALSE if $var exists and has a non-empty, non-zero value. Otherwise returns TRUE.

	The following things are considered to be empty:

	      o "" (an empty string)

	      o 0 (0 as an integer)

	      o 0.0 (0 as a float)

	      o "0" (0 as a string)

	      o NULL

	      o FALSE

	      o array() (an empty array)

	      o $var; (a variable declared, but without a value)

CHANGELOG

       +--------+---------------------------------------------------+
       |Version |						    |
       |	|						    |
       |	|		     Description		    |
       |	|						    |
       +--------+---------------------------------------------------+
       | 5.5.0	|						    |
       |	|						    |
       |	| empty(3) now supports  expressions,  rather  than |
       |	| only variables.				    |
       |	|						    |
       | 5.4.0	|						    |
       |	|						    |
       |	|  Checking  non-numeric offsets of strings returns |
       |	| TRUE. 					    |
       |	|						    |
       +--------+---------------------------------------------------+
EXAMPLES

       Example #1

	       A simple empty(3) / isset(3) comparison.

	      <?php
	      $var = 0;

	      // Evaluates to true because $var is empty
	      if (empty($var)) {
		  echo '$var is either 0, empty, or not set at all';
	      }

	      // Evaluates as true because $var is set
	      if (isset($var)) {
		  echo '$var is set even though it is empty';
	      }
	      ?>

       Example #2

	      empty(3) on String Offsets

	       PHP 5.4 changes how empty(3) behaves when passed string offsets.

	      <?php
	      $expected_array_got_string = 'somestring';
	      var_dump(empty($expected_array_got_string['some_key']));
	      var_dump(empty($expected_array_got_string[0]));
	      var_dump(empty($expected_array_got_string['0']));
	      var_dump(empty($expected_array_got_string[0.5]));
	      var_dump(empty($expected_array_got_string['0.5']));
	      var_dump(empty($expected_array_got_string['0 Mostel']));
	      ?>

	      Output of the above example in PHP 5.3:

	      bool(false)
	      bool(false)
	      bool(false)
	      bool(false)
	      bool(false)
	      bool(false)

	      Output of the above example in PHP 5.4:

	      bool(true)
	      bool(false)
	      bool(false)
	      bool(false)
	      bool(true)
	      bool(true)

NOTES

       Note

	      Because this is a language construct and not a function, it cannot be called using variable functions.

       Note

	       When using empty(3) on inaccessible object properties, the __isset() overloading method will be called, if declared.

SEE ALSO

       isset(3), __isset(), unset(3), array_key_exists(3), count(3), strlen(3), The type comparison tables.

PHP Documentation Group 														  EMPTY(3)