php man page for eval

EVAL(3) 								 1								   EVAL(3)

eval - Evaluate a string as PHP code

SYNOPSIS
       mixed eval (string  $code)

DESCRIPTION
	Evaluates the given $code as PHP.

       Caution

	       The  eval(3)  language construct is very dangerous because it allows execution of arbitrary PHP code.  Its use thus is discouraged.
	      If you have carefully verified that there is no other option than to use this construct, pay special attention not to pass any  user
	      provided data into it without properly validating it beforehand.

PARAMETERS
	      o $code
		- Valid PHP code to be evaluated.  The code mustn't be wrapped in opening and closing PHP tags, i.e.  'echo "Hi!";' must be passed
		instead of '<? echo "Hi!"; >'. It is still possible to leave and reenter PHP mode though using	the  appropriate  PHP  tags,  e.g.
		'echo  "In  PHP  mode!";  ?>In	HTML  mode!<? echo "Back in PHP mode!";'.  Apart from that the passed code must be valid PHP. This
		includes that all statements must be properly terminated using a semicolon.  'echo "Hi!"' for example will cause  a  parse  error,
		whereas 'echo "Hi!";' will work.  A return statement will immediately terminate the evaluation of the code.  The code will be exe-
		cuted in the scope of the code calling eval(3). Thus any variables defined or changed in the  eval(3)  call  will  remain  visible
		after it terminates.

RETURN VALUES
       eval(3)	returns  NULL  unless  return is called in the evaluated code, in which case the value passed to return is returned. If there is a
       parse error in the evaluated code, eval(3) returns FALSE and execution of the following code continues normally.  It  is  not  possible	to
       catch a parse error in eval(3) using set_error_handler(3).

EXAMPLES
       Example #1

	      eval(3) example - simple text merge

	      <?php
	      $string = 'cup';
	      $name = 'coffee';
	      $str = 'This is a $string with my $name in it.';
	      echo $str. "
";
	      eval("$str = "$str";");
	      echo $str. "
";
	      ?>

	      The above example will output:

	      This is a $string with my $name in it.
	      This is a cup with my coffee in it.

NOTES
       Note

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

       Tip

	      As  with anything that outputs its result directly to the browser, the output-control functions can be used to capture the output of
	      this function, and save it in a string (for example).

       Note

	       In case of a fatal error in the evaluated code, the whole script exits.

SEE ALSO
       call_user_func(3).

PHP Documentation Group 														   EVAL(3)